Question

8. (3) Let total work be 360 units. ( therefore A ) and ( B^{prime} s ) work efficiency ( =frac{360}{75}=5 ) unit/day
( B ) and ( C ) 's work efficiency ( =frac{360}{120}=3 ) unit/day
( A ) and ( C ) 's work efficiency ( =frac{360}{90}=4 ) unit/day
Now,
( A, B ) and ( C^{prime} s ) efficiency ( =frac{5+3+4}{2}=6 ) unit/day
Thus, time taken by ( A, B ) and ( C ) to complete the work ( =frac{360}{6}=60 ) days

# 8. A and B can do a piece of work in 72 days. B and C 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? (1) 80 days (2) 100 days (3) 60 days (4) 150 days

Solution