Question

Aand B can do a piece of work in 12 days,B and C on15 days,C and A in 20 how long will each take separately to do the same work?

Answer 1

A+B=12 days......equation (i)
B+C=15 days......equation (ii)
C+A=20 days......equation (iii)
in equation (i)
A+B=12
or,A=12-B
putting the value of A in equation (iii)
C+A=20
or,C+12-B=20
or,C=8+B
putting the value of C in equation (ii)
B+C=15
or,B+8+B=15
or,B=3.5
putting the value of B in equation (i)
A+B=12
or,A=12-3.5=8.5
putting the value of A in equation (iii)
C+A=20
or,C=20-8.5=11.5
Ans: separately A,B and C complete the same piece of work in 8.5 days, 3.5 days and 11.5 days respectively.