Question

can do a job in 72 days. B and C can do the same job
30 days, and A and C can do the same job in 90 days. In
how many days will all the three take to complete the job? Solution
80 days
b. 100 days
C 60 days
d. 150 days​

Answer 1

your complete question -> A and B can do a piece of work in 72 days. B and C can do it in 120 days, A and C can do it in 90 days. In how many days all the three together can do the work ?

[A]150 days

[B]60 days

[C]80 days

[D]100 days

solution : given, A and B can do a job in 72 days

B and C can do the same job in 120 days

C and A can do the same job in 90 days

A and B can do 1/72 part of work in a day.

similarly, B and C can do 1/120 part of work in a day and C and A can do 1/90 part of work in a day.

then, (A + B) + (B + C) + (C + A) = 1/72 + 1/120 + 1/90

or, 2(A + B + C) = (5 + 3 + 4)/360

or, 2(A + B + C) = 12/360 = 1/30

or, A + B + C = 1/60

hence, all the three together can do the work in 60 days

hence, option (B) is correct choice .