Answer:
1.87 days
Explanation:
If it takes 20 men can make a road for 50 km in 10 days, by the unitary method, 1 man can make 50 km/20 in 10 days.
So 1 man can make 2.5 km in 10 days.
We then calculate for 15 men by multiplying the expression by 15
So, for 15 men, 15 × 1 man can make 2.5 km × 15 in 10 days/
So, 15 men can make 37.5 km in 10 days.
Since 15 men can make 37.5 km in 10 days, 15 men will make 1 km in 10/37.5 days.
So multiplying by 7,
15 men will make 7 × 1 km in 7 × 10/37.5 days
Thus 15 men will make 7 km in 1.87 days