the OA is 2^8
but how do you get that?
you cant just subtract and then square the exponents, that's incorrect.. So how is the answer 2^8?
I know it's certainly not
2^(4-1)^2 = 2^3^2 = 2^9
Another exponents problem from the official CAT practice
This topic has expert replies
Source: Beat The GMAT — Problem Solving |
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GMATpaduan
- Newbie | Next Rank: 10 Posts
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You CAN just subtract and square the exponents.
2^(4-1)^2
Take care of the info in the parentheses first: = 2^(3)^2
= 2^9...
2^3-2 = 2^3 / 2^2 = 2^1
Therefore 2^9/2^1 = 2^8
Proof for: 2^3^2 being equal to 2^9
2^(3)(3) IS the same as 2^3^2, in both cases the answer is 2 ^9 - take care of the exponent first, and then calculate.
2^(4-1)^2
Take care of the info in the parentheses first: = 2^(3)^2
= 2^9...
2^3-2 = 2^3 / 2^2 = 2^1
Therefore 2^9/2^1 = 2^8
Proof for: 2^3^2 being equal to 2^9
2^(3)(3) IS the same as 2^3^2, in both cases the answer is 2 ^9 - take care of the exponent first, and then calculate.
GOOD LUCK ALL!
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thumpin_termis
- Senior | Next Rank: 100 Posts
- Posts: 60
- Joined: Fri Jun 01, 2007 11:02 pm
I believe the key here is that:
(2^3)^2 is NOT equal to 2^3^2
Remeber PEMDAS for calculating order:
(2^3)^2 = (2^3) x (2^3) = 2^6
2^3^3 = 2^(3^3) = 2^9
In this question's case, it's the latter, so
(2^9)/2 = 2^9 - 2^1 = 2^8
So I also vote for A) 2^8.
(2^3)^2 is NOT equal to 2^3^2
Remeber PEMDAS for calculating order:
(2^3)^2 = (2^3) x (2^3) = 2^6
2^3^3 = 2^(3^3) = 2^9
In this question's case, it's the latter, so
(2^9)/2 = 2^9 - 2^1 = 2^8
So I also vote for A) 2^8.
