Solution:
Given:
5 men and 8 women can complete a task = 34 days
4 men and 18 women can complete the same task = 28 days
Formula:
Total work = Efficiency × Time
Calculation:
Let efficiency of 1 man and 1 woman be x and y respectively, then
(5x + 8y) × 34 = (4x + 18y) × 28
⇒ (5x + 8y) × 17 = (4x + 18y) 14
⇒ 85x + 136y = 56x + 252y
⇒ 85x - 56x = 252y - 136y
⇒ 29x = 116y
⇒ x/y = 116/29
⇒ x : y = 4 : 1
Total work = (5 × 4 + 8 × 1) × 34
Total work = (20 + 8) × 34
Total work = 28 × 34
Efficiency of 3 men and 5 women in 1 day = (3 × 4 + 5 × 1) = 12 + 5 = 17
∴ Time taken by 3 men and 5 women to complete the whole work = (28 × 34)/17 = 56 days