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Re: If a = 3^(b – 1), what is the value of a + b ?
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04 Nov 2014, 10:42

1

Statement 1 tells that 3^b+2 = 3^5 so b=3, and a = 9. Sufficient.

Statement 2 tells that a = 3^2b-4. From the stem we know that a=3^b-1, so 3^2b-4 = 3^b-1 --------> (3^2b-4)/ (3^b-1) = 1 (b/c they are equal to each other and no expression can equal zero) -------> 3^2b-b-4+1 = 1 ------> 3^b-3=1 so b=3 and a=9. Sufficient. Answer is D.

WE: General Management (Non-Profit and Government)

Re: If a = 3^(b – 1), what is the value of a + b ?
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04 Nov 2014, 21:05

1

Given a=3^(b-1) .......(1)

1) 3^(b+2)=243=3^5 so , b +2=5 & b=3

Inserting the value of b in equation (1) one can get the value for 'a', which will further give the complete value for a+b. SUFFICIENT.

2) a=3^(2b-4) From equation (1) we can say : 3^(2b-4)=3^(b-1) so, 2b-4=b-1 b=3 Again value for 'a' can be found from any of the equations above and one can can easily obtain the complete value for a+b. SUFFICIENT.