Question

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

11th - 12th Class

Maths

Solution

275

4.0 (1 ratings)

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