Kusum, Joy and Mona together can complete a piece of

Solution

Let’s assume the total work is 480 units. Joy alone can do the same piece of work in 120 days. Efficiency of Joy = 480/120 = 4 units/day The efficiency of Kusum is 25% less than the efficiency of Joy. efficiency of Kusum = (100-25)% of 4 = 75% of 4 = 3 units/day The efficiency of Kusum is 62.5% less than the efficiency of Mona. 3 = (100-62.5)% of efficiency of Mona 3 = 37.5% of efficiency of Mona 3 = 0.375 x (efficiency of Mona) efficiency of Mona = 8 units/day Kusum, Joy and Mona together can complete a piece of work in (y-18) days. (3+4+8)x(y-18) = 480 15x(y-18) = 480 (y-18) = 32 y = 32+18 y = 50 Time taken by Kusum alone to complete the same piece of work alone = 480/3 = 160 days = (3y+10) days