Posted by **majumder** on Thursday, April 26, 2012 at 10:20am.

A does 8/15 of a work in 8 days and the remaining work is finished with the assistance of B in 4 days . how long will B take to do the work alone

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**Reiny**, Thursday, April 26, 2012 at 11:36am
A's rate = (8/15)W / 8 = W/15

let B's rate = W/x , where x is the time it would take B to do the job

combined rate = W/15+W/x = (Wx + 15W)/(15x)

then 4(Wx + 15W)/(15x) = (7/15)W

divide by W and expand

(4x + 60)/(15x) = 7/15

times 15

(4x+60)/x = 7

multiply by x

4x + 60 = 7x

x = 20

it would take B 20 days

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