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no system

by rupsk » Tue Sep 06, 2011 7:48 am
A number when divided by a certain divisor left a remainder of 14 but when then the number was multiplied by 6 and then divided by the same divisor the remainder was 15. Find the divisor if it leaves a remainder of 7 when divided by 8.


A. 23


B. 55


C. 87

D. 47

E. 49
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by gmatclubmember » Tue Sep 06, 2011 8:01 am
rupsk wrote:A number when divided by a certain divisor left a remainder of 14 but when then the number was multiplied by 6 and then divided by the same divisor the remainder was 15. Find the divisor if it leaves a remainder of 7 when divided by 8.

A. 23
B. 55
C. 87
D. 47
E. 49
---------------
let the no. be N, the quotient be q1 when divided by divisor d to leave a remainder of 14. so we have
N =d*q1+14-------first cond.
6N=d*q2+15--------second cond.
d=8*q3+7----- third cond.

now substitute N from first cond in second cond. and u get...
6d*q1+84 = d*q2+15 =>d(-6q1+q2) = 69 => d*q4=69, so d either can be 1 or 3 or 23. But q3 can be positive only when d is 23 (from third cond.) so the divisor has to be 23.

A. would be the answer.

Cheers
Ami/-