collection of tough problems from G PREP - 9

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Source: — Data Sufficiency |

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by sanju09 » Sat Feb 06, 2010 5:35 am
abhasjha wrote:If a, b, and c are integers, what is the value of a?

(i) (a-7)(b-7)(c-7) = 0

(ii) bc = 18
(1) Here, it can be true even if a is not 7, and any one of b and c or both, is 7. So, when a is not 7, what's a? Still unsolved. Insufficient

(2) This tells absolutely nothing about a. Insufficient

Taken together

Neither b nor c can take the value 7, as these are integers and their product is 18, which doesn't have 7 as a factor. Hence, x can only be 7 in order to prove info in (1), as true. Sufficient

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by ajith » Sat Feb 06, 2010 8:41 am
abhasjha wrote:If a, b, and c are integers, what is the value of a?

(i) (a-7)(b-7)(c-7) = 0

(ii) bc = 18
1) a or b or c =7

insufficient

2) bc =18 - insufficient

combining

b and c are not 7

hence a =7

sufficient
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