Problem: Rahim drives from Jessore to Chaudanga in 45 minutes. The road between Jessore and Chaudange is 48 km. long and it consists of \both rough and good surfaces. Where the surface is good, Rahim drives at 72 km/hr; and where the surface is bad, he drives at 48 km/hr. Find the number of kms of good surface.

Correct Answer: 36 Kms

Explanation:

Let, Rahim drives x km. at 72 km/h

(48 —x) km is driven at 48 km/h

According to question$\frac{x}{72}$ + $\frac{48-x}{48}$ = 45 x $\frac{1}{60}$ = $\frac{3}{4}$

=> $\frac{2x + 3(48-x)}{144}$ = $\frac{3}{4}$

=> $\frac{144-x}{36} = $\frac{3}{4}$$

=> —x=—36

=> x=36