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How is this statement sufficient?

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Source: — Data Sufficiency |
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by albatross86 » Fri Jul 09, 2010 2:45 pm
The question stem gives us: 2^(2m + 1) = 2^(n + 2)

=> 2m + 1 = n + 2
=> 2m - n = 1

1. 3n - 1 = 8
=> n = 3

=> 2m = 1 + n = 4 => m = 2

=> m + n = 5 ... SUFFICIENT


2. m + 2n = 8 => m = 8 - 2n

Substitute in our question stem eqn:

2(8 - 2n) - n = 1
=> 16 - 4n - n = 1
=> 5n = 15
=> n = 3.... SUFFICIENT

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by amirp » Fri Jul 09, 2010 2:52 pm
ohhh,,, i totally forgot about the equation in the question stem... ugh,,, got it... thanks alot
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by Haaress » Fri Jul 09, 2010 2:52 pm
What do we have: 2m +1 = n + 2 or 2m - n = 1
What do we need: m + n?

Stmt 1: provides the value of n , so we can get the value of m and thus the value of m + n. Suff.

Stmt 2: m + 2n = 8 but remember that we already know that 2m - n =1, so we can solve the values of m and n from the simultenoues eqns or system of eqns. Thus, suff.

Hope that helps.
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