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Time & Work

A, B and C can do a piece of work in 15, 20 and 30 days. They undertake to complete the work for Rs. 810. How much share of A exceeds that of B ?

Option:
A. Rs. 90
B. Rs. 180
C. Rs. 270
D. Rs. 360
Answer: A . Rs. 90

Justification:

A's 1 day's work = $1/50$
B's 1 day's work = $1/20$
C's 1 days's work = $1/30$
Ratio of their shares = $ 1/15:1/20:1/30$ = 4 : 3 : 2 
Thus, A's share in Rs. 810
=Rs. $4/9$ x 810 = Rs. 360
and, B's share in Rs. 810.
=Rs. $3/9$ x 810 = Rs. 270
Hence, difference between their shares = Rs. (360 - 270) = Rs. 90.

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