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Cube root of 80 =? How well do you understand numbers and roots in math?

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TabletClass Math

TabletClass Math

Күн бұрын

How to find the cube root of a number without a calculator - radicals and square roots. Learn more math at TCMathAcademy.....
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Пікірлер: 83
@lyndafjellman3315
@lyndafjellman3315 2 ай бұрын
I do not ever remember being taught this clever trick!! And you showed me how to figure it out on my basic calculator. Double win. I never need to figure cube roots, but it is nice to know how.
@nyneeveanya8861
@nyneeveanya8861 2 ай бұрын
Took a guess. My thinking? Cube root of 8 is 2 . 8 x 10 =80 so answer is 2 x cube root of 10 and that’s D.
@davidreidenberg9941
@davidreidenberg9941 Ай бұрын
Yo are absolutely correct. Also, the other answers cannot possibly be correct.
@BluesChoker01
@BluesChoker01 15 күн бұрын
@@nyneeveanya8861 yep. This works because the root of a number equals the product of the roots of it's factors. So solving using root3(8) * root3(10) works as well obtaining all the prime factors (root3(2) * root3(2) * root3(2) * root3(2) * root3(5)) and is quicker. But yeah, best to read the problem a couple of times in case he wants all the factors. :-) Eric Had a track coach who also taught math. After running enough 400 meters to puke, he'd start asking us about that night's homework! Had some Voodoo Mojo working, because we learned his math and improved our running. And learned how to hurl for distance and accuracy. 😜
@frowe327
@frowe327 2 ай бұрын
Excellent coverage of this problem John ! Very well explained!
@erembald2927
@erembald2927 2 ай бұрын
Did it in my head thanks to all the practice i'm now getting. 80^(1/3) = (10 x 8)^(1/3) = 2 x 10^(1/3)
@filicruz7566
@filicruz7566 2 ай бұрын
😊 3:57 3:58 😊
@BluesChoker01
@BluesChoker01 18 күн бұрын
Nicely reasoned and splained😊❤
@DrDoom76
@DrDoom76 Ай бұрын
I've taught both my kids to show their work with math. HOWEVER, if you're faced with a multiple choice question on a test, there's a good chance you can work the problem backward and find the most likely answer (helped my daughter increase her SAT score by 80 points on the 2nd try -- 1240 to 1280). A) 8 --> 8^3 does not equal 80 B) root 2--> (root2)^3 does not equal 80 C) cuberoot 16--> see B so A, B, C are eliminated which leaves D as the most likely answer. The only caveat is when the teacher puts option E) None of the above. THEN you have to do the math and know (dang it Mr. Johnson, you always tripped me up that way...but it did help teach me the math)
@froufrou4172
@froufrou4172 2 ай бұрын
What I would like to know is: what is the practical application of cube root? Where is it used it in real life?
@tomtke7351
@tomtke7351 2 ай бұрын
I GET IT! You seldom have to take cube root to: (-1-) change TV channel, although there's likely some equation that predicts the coverage the remote has. (-2-) To set the temperature of the thermostat, although the predictive capability of modern thermostats might need cube roots. (-3-) The automobile?? With over 30 different onboard computers, who knows whether a car need cube root. IN FACT... The volume (V) of a CUBE is side×side×side. Therefore, given that volume = X the side dimension is: X = Cuberoot(V)
@devonwilson5776
@devonwilson5776 2 ай бұрын
Greetings. There are many applications for which the cube root would be required, engineering, mechanical and electrical, construction, and medicine.
@tomtke7351
@tomtke7351 2 ай бұрын
HERE GOES -- a previous problem about --> a cone shaped glass vs height of fluid of in glass. The proof to be achieved is that glass filled to 80% height contains 50% of volume.. The volume of cone is: V = (1/3)(pi)(r^2)(h) By similar triangles the h and r of the cone are related such that: h.1/r.1 = h.2/r.2 Restated: If h is 80% then r is 80% Incorporating into equation: V.full = (1/3)(pi)(r)(h) V.50%= (1/3)(pi)(xr^2)(x.h) = (1/3)(pi)(x^3)(r)(h) Since V.full = 2•V.50% (V.50%/V.full) = 0.5 Then 0.5= (x^3•pi•r^2•h)/(pi•r^2•h) 0.5= x^3 SO..... x = cube-rt(0.5) = 0.7937 =~ 80%
@KarlSnyder-jh9ic
@KarlSnyder-jh9ic 2 ай бұрын
For example, the equation for Kepler's Third Law is P² = a³, so the period of a planet's orbit (P) squared is equal to the length of the semi-major axis of the orbit (a) cubed.
@BluesChoker01
@BluesChoker01 18 күн бұрын
How about our two great 400M Hurdlers, Sidney Mac and Anna Cockrell? Another WR for Sidney, and Cockrell was less than a second behind Sidney. Gabby Thomas blazed the curve and scorched the straight for gold. Rai Benjamin took his first gold it in the 400m hurdles as he raced past the Swedish WR holder missing a new WR of his own by just 0.30 seconds. And in an effort I've never seen, Quincy, ran a poor 2nd curve to trail 5 runners with 50 meters to go. Somehow, tight, with no form left, he passed five good Olympians and just leaned enough for the gold. I've never seen someone so spent, absolutely command his body to do what seemed absolutely impossible. And, as icing, his time was 3rd fastest in history: 43.29 seconds. I ran the 400m in HS and College, and know why they call this race the Beast. It doesn't matter how much stronger, faster and smarter you get, the point is to sprint faster and longer than humans we're really made to run. The training can help estimate when you're going to hit the "wall," but it's going to find everyone. But every once in awhile, it hits at the wire and you set a new PR. For once, you've tamed the Beast. Except for Sidney, she must be an Alien😊❤ As to the dimension question: We must calculate stuff in our universe with our limited senses and brains. As we experience only 3 spatial dimensions and 1 temporal one (time), we use these. Of course, we could be entirely wrong. But until we develop more senses and brain parts, and they way many folks behave, we might not be around long enough to see that‼️ BTW, theoretical physicists developed a model the dimensions of our Universe in the late 90s that uses 11 dimensions. Most are aren't detectable, so are just a mental exercise. I can see the need to stretch our minds, as that's how we stumble into new realities, but if you can't see or measure something with an experiment, it's mere speculation. This was another attempt to find a Grand Unification Theory or Gut, which unites our two greatest theories which have explained the mechanics of both large and small objects in our universe, except for some aspects of gravitation: Quantum Mechanics and General Relativity. Both explain and predict behaviors almost perfectly and have been confirmed experimentally for 100 years. But there exists a hole in each, which makes them each partial theories. This means that there is an unexplained Hidden Reality. When both theories attempt to describe the nature of black holes, which we can see to their event horizons, beyond which light photons can't escape the gravitational warpage of spacetime - often called a gravity well, both theories spit out odd but similar results. Each theory calculates the radius as an infinity or series of infinities. While useful in limits, infinite results on finite systems are not very helpful. We can see the affects of black holes on stars and such around them, and they appears to have finite diameters. The missing parts seem to involve a deeper understanding of a still undetected particle predicted by Einstein, which also should be part of the Standard Model of Physics for a Quantum Theory of Gravity. This missing criter, is a Boson, or force carrying particle, and probably has no mass. A more familiar Boson is the massless Photon, which is responsible for carrying the electromagnetic force or light. We see objects in our narrow wavelength/frequency band when photons contact the Red, Green, and Blue cones in our retinas. The colors we see are created by our occipital lobes at the back of our skulls. Red, Green and Blue colors can be mixed to allow us to see billions of colors. You've probably heard of RGB with respect to certain monitors. They use circuitry to simulate the color mixing our brains do. Too bad we don't have Raptor vision of our Eagles and other birds of prey. Not only can the see close and far (eg a hare running from half a mile above and a mile behind), but they see a wider band of colors. They can see into the near ultraviolet and into the other side of the infrared. One last bit of info. The JWST, looks in several bands, but primarily in the infrared, and deep infrared. We experience this as thermal heat. But it has a longer wavelenth than visible, ultraviolet, xRays and Gamma rays. This longer wavelength can pass through most seller gas and dust to see light within and behind it. Most of the light from the early universe has cooled over billions of years and is mostly in infrared or microwave wavelengths. To allow the 21-foot gold plated mirrors to see this light, the infrared from earth and sun are blocked by shields. This allowed the temperature of JWST to cool about 2°C, the ambient temp of interstellar space. And boy have we seen stuff we didn't expect. Early galaxies more defined, which more mature stars. Clearly, the universe cooled enough for matter like hydrogen and helium to coelesce and stars to form, ignite and spread their nuclear light into the cosmos, faster than previously thought. Eric
@normanmunns4743
@normanmunns4743 2 ай бұрын
The cube root if 80 is 4 point something. The answer must be d which is 2 x 2 point something which is likely to be 4. Something
@linsqopiring6816
@linsqopiring6816 2 ай бұрын
I like this way of thinking also.
@BasementEngineer
@BasementEngineer 2 ай бұрын
That's how I solved it.
@linsqopiring6816
@linsqopiring6816 2 ай бұрын
11:10 "1/3 * 3 is of course 3"
@johnnyragadoo2414
@johnnyragadoo2414 2 ай бұрын
I've gotten nutty for logs. The log of the cube root of 80 is log(80)/3. Since 8*10 is 80, and since adding logs is multiplying, the log of the cube root of 80 is also (log(8)+log(10))/3, or log(8)/3 + log(10)/3. Since dividing a log by 3 gets the log of the cube root, log(8)/3 = log(2). The log of the cube root of 80 is log(2)+log(10)/3. Since log(10) is 1, the log of the cube root of 80 is log(2)+1/3. 10^(log(2)+1/3) is the same as (10^log(2))*(10*1/3), or 2 times the cube root of ten, just like the video's answer. Checking my answer log(2)+1/3 times three should be the log of 80. So 3*log(2) plus one is about 1.9. Raise 10 to that power and you get 80. Heh, heh, heh...
@rickhole
@rickhole 2 ай бұрын
You tempt me to get out my slide rule and see if I can remember how to do it on that. But the slide is stuck. First I'd have to figure out how to restore it.
@johnnyragadoo2414
@johnnyragadoo2414 2 ай бұрын
@@rickhole That sounds like a good project. Interestingly, I see the cube root of 80 can also be expressed as 20*cube root of 0.01. 2*cuberoot(10) = 4*cuberoot(1.25) = 20*cuberoot(0.01). 0.01 is 1 * 1/100, so you can move the "1" outside the radical as its cube root, which is one - so you're stuck at 20*cuberoot(0.01). You could also say that equals 20*cuberoot(64*.01/64). That means the cube root of 80 =80 * cuberoot(.01/64). I think at this point I'll leave the rabbit hole to someone else! 🙂
@johnnyragadoo2414
@johnnyragadoo2414 2 ай бұрын
Dang, this is interesting. 80 * cuberoot(.01/64) is food for thought. .01/64 is 4^-3 * .01. 4^-3 can move outside the radical by dividing instead of multiplying. 80*cuberoot(4^-3 * .01) becomes 20 * cuberoot(.01), which was what I was at a few steps ago. But what about solving cuberoot(16*5)? When you move 2^3 outside of a cube root radical, you're multiplying the radical by 2^(3/3). The numerator was from what it was inside the radical, the denominator is the power you're reducing it by. So, cuberoot (16*5) becomes cuberoot(4^2*5) which becomes 4^(2/3) times cuberoot of 5. In that term, 4^(2/3), the two is from the "2" power of 4 inside the radical and the denominator is from the "3" on the radical itself. Intriguing that 4^(2/3) times 5^(1/3) is the cube root of 80. It seems like there should be something to be done with that 2/3 and 1/3.
@BluesChoker01
@BluesChoker01 22 күн бұрын
Hi guys, Need to check your log rules. For example, given the Exponential equation below, Log 3 is the exponent we raise Base 10 to equal 3. 10^x = 3 ✅ Exp Form log 10^x = log 3 x log 10 = log 3 x = log 3 log 10 x = log 3 = 0.4771 ✅ log form Also, the power rule of logs requires you to move the power, as it is (integer, variable, rational number), in front of the log. And you must take the logs of *both* sides when you use it. This question asked us to simplify an expression. It really wasn't an equation, although you could assume John's question mark was a variable. 😅 Simplification: 80^(1/3)❓ ((2^4) * (5))^(1/3) ((2^3))*(2)*(5))^(1/3) 2*(2*5)^(1/3) 2*(10)^(1/3) == 4.3089✅
@johnnyragadoo2414
@johnnyragadoo2414 22 күн бұрын
@@BluesChoker01 Did I get anything wrong?
@russelllomando8460
@russelllomando8460 2 ай бұрын
got it D easy math 8 x 10 = 80 cube rt of 8 is 2 thanks for the fun
@bigdog3628
@bigdog3628 2 ай бұрын
super simple. We know that 8 is a perfect cube and 8 * 10 is 80. So the answer must be 2 * 10^(1/3) which is answer d. When you have an exponent that is a fraction, the numerator is the power and the denominator is the root. so √x is the same as x^(1/2).
@raya.pawley3563
@raya.pawley3563 2 ай бұрын
Thank you
@laobernadus5743
@laobernadus5743 2 ай бұрын
D --->>> ( 2 root 3 )
@dbird1356
@dbird1356 Ай бұрын
D. 2x Cube root of 10.
@shakirhamoodi5009
@shakirhamoodi5009 29 күн бұрын
d) 2 * (10)^(1/3)
@KW-gb9cd
@KW-gb9cd 2 ай бұрын
8 is 2 x 2 x 2, so 80 is 2^3 x 10; the answer is d.
@user-gl7co5oi7d
@user-gl7co5oi7d 2 ай бұрын
Answer is d)
@johnmarchington3146
@johnmarchington3146 Ай бұрын
The Answer is (d) Cube root of 80 is cube root of 8 x cube root of 10
@samswift4921
@samswift4921 2 ай бұрын
D, although A is closr.
@giannaleoci2328
@giannaleoci2328 2 ай бұрын
rc80=rc(2^3•10)=2•rc10
@thecalculator80
@thecalculator80 10 күн бұрын
Why is the cube root of 10"simpler" than the cube root of 80? I am no closer to knowing what is the cube root of 80, which was the original question! Let's start a brand new problem to solve: what is the cube root of 10? Do THAT in your head!
@richardhole8429
@richardhole8429 2 ай бұрын
While I could have easily solved this, instead I looked at the choices. A too large, B, C too small therefore choose D. When I looked at the D choice I knew it to be correct, 2^3 = 8, 8 × 10 = 80 QED.
@walter71342
@walter71342 2 ай бұрын
When dealing with timed/multiply choice question eliminate incorrect answers and move on. A,B and C are all to small so the answer must be D. What is the next question!
@rickhole
@rickhole 2 ай бұрын
@@walter71342 That's what I taught my grandson facing a multiple choice college entry exam. I had taken so many of those multiple choice, timed tests that doing as you say is the first choice, not the last.
@terry_willis
@terry_willis 2 ай бұрын
a) 8 is too big. Has to be between 4 and 5. b) and c) are too small.
@jpbobinus1377
@jpbobinus1377 2 ай бұрын
2 squarout 10
@kermitefrog64
@kermitefrog64 Ай бұрын
I would guess that it is "d".
@Darisiabgal7573
@Darisiabgal7573 2 ай бұрын
CBRT(80)= itself But if you insist on deconstructing it we can do several things to it CBRT(80) = CBRT(8000/1000) = 20/CBRT(100) = 20 * CBRT(100)*CBRT(100) /1000 = 0.2 * CBRT(10000) That’s one way we could make it look funny We could multiply the top and bottom by 10 = CBRT(10000) *2 /10 = CBRT(10000/1000) * 2 = 2 * CBRT(10) Without using a calculator and completely solving the problem 2^3 = 8 and 3^2 = 27. Let’s change the volume scale so volume = 10000 What cubed gives 10,000. 25*25 = 625 * 25 = 15625 22*22=484 * 11 gives 5324 * 2 = 10648 21*21=441 * 21 = 8820+441= 9261 Thus our first approximation is 2x 2.15 = 4.30 Let’s rescale to 1000000 and so our volume is 10,000,000 215x215 = 1075 + 2150 + 43000 = 46225 46225 x 215 = 462250 + 231125 + 9245000 = 9938,375 So the slope of a x at two positions I’d f’(x) in this case x^3 = 3x2 We are at 9938375 but want to be 1000000 so we need 61,625 Taking a full step up would be adding 138625+ bit more. We only need to move up about one half of this. So guessing 215.45 so dividing by CBRT million I get 2.1545 * 2 = 4.309. 4.309
@BluesChoker01
@BluesChoker01 18 күн бұрын
Now, that's how Mr. KZfaq MethMan would do it😂😂❤️
@jameskelley3365
@jameskelley3365 Ай бұрын
d
@yanamadalabhanuraju6721
@yanamadalabhanuraju6721 25 күн бұрын
D
@dwaipayandattaroy9801
@dwaipayandattaroy9801 2 ай бұрын
8, not an option, √2 same, cuberoot 16 also same, 2 and cuberoot of 10 is the correct one.
@silviodias7540
@silviodias7540 2 ай бұрын
RC 80 ? RC 16x5 = RC 2^3x2x5 = 2 RC 2x5 = 2 RC 10, opção d)
@areeratasudhasirikul952
@areeratasudhasirikul952 2 ай бұрын
2 cube root10=d
@mr.mxyzptlks8391
@mr.mxyzptlks8391 2 ай бұрын
I’ll latch on to the multiple choice test. Obviously, figure out the correct answer. If one is really lost, take an educated guess. Then probability kicks in, in this case in your favor, I think. . Not checking any answer = 0 points. Independent of the number of answers, any choice is better than no choice (I think there is a theorem behind this). But, know your teacher. In university, I had one , ONE, professor who used multiple choice. And a false answer would result in -x points. I think this is pedagogically incorrect, but that class luckily wasn’t mandatory for my degree, and yes, I passed it. But my sentiment remains…
@carlosamezquita1203
@carlosamezquita1203 2 ай бұрын
√80 cúbica =2√10 cúbica
@chrisdissanayake6979
@chrisdissanayake6979 2 ай бұрын
d)
@ernieborja221
@ernieborja221 19 күн бұрын
D 2 ³_/10
@lorettamertz2800
@lorettamertz2800 2 ай бұрын
After ten, I have to take off my shoes.
@TheREALDocRabbit
@TheREALDocRabbit 2 ай бұрын
D, it's obvious...
@BanksfMax
@BanksfMax 2 ай бұрын
😊 A+ but I guessed it
@playgirl7305
@playgirl7305 2 ай бұрын
Da was immediately obvious because the other options are to small.
@gavindeane3670
@gavindeane3670 2 ай бұрын
B and C are too small. A is too big.
@playgirl7305
@playgirl7305 2 ай бұрын
@@gavindeane3670 you are right, my mistake!
@mylittlepitbull3143
@mylittlepitbull3143 2 ай бұрын
First genius . Two times the cube root of 10. 4th grade math
@jald910
@jald910 2 ай бұрын
I got it too, but at least when I was in the 4th grade long long ago, we had no concept of cube roots, let alone how to simplify them
@mylittlepitbull3143
@mylittlepitbull3143 2 ай бұрын
@@jald910 I was just cappin.
@ErvanKatari-sb5gp
@ErvanKatari-sb5gp 2 ай бұрын
You are truly doing a major disservice to anyone trying to learn math for whatever their intended purpose; because you did not teach/show the viewer how to solve the "Problem" or "Call of Question", you shared a shmorgishborg of math properties, principles, and methods and at the end of watching your video I do not believe you know how to solve the problem and used an answer Key. There is no way that you would be able to complete that equation with a number and then put it back into an equation. But um teaching individuals to eliminate answers in the method you did is just AWFUL and you should be banned from KZfaq.
@scimitar415
@scimitar415 2 ай бұрын
just curious .......was mr. utube mathman vaccinated with a phonograph needle ?
@rajeshvyas934
@rajeshvyas934 2 ай бұрын
d
@alessioandreoli2145
@alessioandreoli2145 2 ай бұрын
D
@sekharb6651
@sekharb6651 2 ай бұрын
d
@josephlaura7387
@josephlaura7387 2 ай бұрын
d
@JasmineDaisy111
@JasmineDaisy111 2 ай бұрын
d
@sigeliu4256
@sigeliu4256 2 ай бұрын
D
@raocm979
@raocm979 2 ай бұрын
D
@farjanajahan3222
@farjanajahan3222 2 ай бұрын
D
@mawavoy
@mawavoy 2 ай бұрын
D
@subasu478
@subasu478 2 ай бұрын
D
@user-jj3hi3gh4u
@user-jj3hi3gh4u 2 ай бұрын
D
@yebrahbeyene8155
@yebrahbeyene8155 2 ай бұрын
D
@Sailor376also
@Sailor376also 2 ай бұрын
D
@nancyfloyd7052
@nancyfloyd7052 2 ай бұрын
D
@davemojarra2666
@davemojarra2666 2 ай бұрын
D
2 to the x = 9, many don’t know where to start
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