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by sanju09 » Tue Jul 27, 2010 4:50 am
If the average of 2, 11, b, 34 is greater than 17, what is the value of 'b'?
(1) Average of 41, b, 53, 61 is less than 46.
(2) 'b' is a prime number.

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Source: — Data Sufficiency |

by nicolezl » Tue Jul 27, 2010 5:17 am
From the problem, we know that (2+11+b+24)/4 > 17, which simplifies to b > 21.

(1) From this we know that (41+b+53+61)/4 < 46, which simplifies to b < 29. All we know is that 21 < b < 29.

Insuff.

(2) b is a prime number greater than 21.

Insuff.

Putting them together, b is a prime number b/w 21 and 29, so b = 23.

Answer is C
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