| | Question 7

A alone would take 64 hours more to complete a work then A + B work together. B take 4 hours more to complete a work alone than A and B work together.Find in how much time A alone complete the work.
(A) 16 hours
(B) 60 hours
(C) 72 hours
(D) 48 hours


Answer: (B)

Explanation: First method
Let A and B take x hours to complete a work together.
A alone would take (x + 64) and B alone would take (x + 4)hours to complete the work.
A( x + 64) = x (A + B)
64A =x B …………(1)
B(x + 4)= x(A + B)
4B = x A……………(2)
from (1)and (2)
64A = x * x A/4
x2 = 256
x = 16
A alone = 16 + 64 = 60 hours

Shortcut method –
x2 = more of A * more of B
x2= 64 * 4
x2= 256
x= 16

Quiz of this Question
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