Question

if a and b done a work i 15 days and only b done this work in 20 days then a done this work in how many days.

Answer 1

a+b=15
b=20
lets take LCM of 20 and 15
it is 60
so, 60 units is the total work to be done
so,
a and b together did(60/15) = 3 units
and b alone did(60/20) = 4 units
so,a does work = 4 - 3 = 1 unit
so, a can do that work in(60/1)days = 60 days

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