18 men or 36 boys working 6 hours a day can plough a field in 24 days. In how many days will 24 men and 24 boys working 9 hours a day plough the same field ?

Answer: Option D

Let the required no of days be x.
18 Men = 36 Boys
1 Man = 2 Boys
∴ 24 Men = 48 Boys
According to the question,
M₁D₁H₁ = M₂D₂H₂
36 × 24 × 6 = (48 + 24) × x × 9
36 × 24 × 6 = 72 × 9 × x
x = $$\frac{36\times 6\times 24}{72\times 9}$$
x = 8 days