GMAT Question of the Day: Problem Solving

V Pat
#1. December 7th, 2006, at 4:42 AM.

(B) 4 and 5

Chirag
#2. December 7th, 2006, at 4:52 PM.

B) for sure

Arun
#3. December 7th, 2006, at 5:17 PM.

B

BornFree
#4. December 22nd, 2006, at 4:27 PM.

b

AP
#5. May 17th, 2007, at 9:25 PM.

b

hari
#6. December 6th, 2007, at 4:09 AM.

b

kms
#7. December 6th, 2007, at 1:01 PM.

#B

ecs
#8. December 6th, 2007, at 3:18 PM.

B#

Senjaya Khoo
#9. December 8th, 2007, at 5:05 PM.

yes using calculator of course 4th root of 496 is 4.72, but how’s the GMATers way?
….
okay, you must try to power the middle answer that’s
5 and 6
and starts with 5 first: 5^4 = 5×5x5×5 = 625 too high, so lower it,
with 4: 4^4 = 4×4x4×4 = 256 too low, so the answer was B between 4 and 5.
Great? oh yeah…

nyn
#10. December 10th, 2007, at 8:23 PM.

(B) 4 and 5

pramod
#11. December 11th, 2007, at 2:57 AM.

4th root is square root of (square root 496)
it implies suare root of 24, since square root of 496 is 24,
therefore answer lies between 4 and 5.

CYN G
#12. April 26th, 2008, at 12:34 AM.

Approach I: Factor out 496 to see what the composition is – use 8 and 31, now apply the

fourth root of 8 times the fourth route of 31, since a root can be broken into a product of

roots.

Now the fourth root of 8 is clear, it is 2. The fourth root of 31 is not, so using concept of roots, I estimate that the fourth root of 31 is around 2.3 because if I multiply it four times it gives me about 28. Hence, 2 time 2.3 = 4.6 (B).

Approach II: Factor out 496 to see what the composition is in terms of multiples, we should get 2 2 2 2 31. Hence, we see that the fourth root of 496 will entail at least 2 and some sort of multiple found in 31. After picking a couple of numbers say 2.3 times 2.3, which is 5.29 then 5.29 times 5.29 which is about 28, I can safely estimate that the fourth root of 31 is close to 2.3. If I use 2.4 times 2.4 times 2.4 times 2.4, this would be greater than 31 which means that it is too high.

shilpa
#13. August 15th, 2008, at 9:12 AM.

B