A bus takes two hours less for a journey of 300 km if its speed is increased by 5 km/hr from its normal speed. The normal speed is

A20 km/hr

B25 km/hr ✓ Correct

C35 km/hr

D50 km/hr

Correct answer: (B) 25 km/hr

Explanation

The normal speed is 25 km/hr.

Let speed = s; then 300/s - 300/(s+5) = 2.

This gives 1500 = 2s(s+5), so s^2 + 5s - 750 = 0.

Factoring: (s - 25)(s + 30) = 0.

The positive root is s = 25 km/hr.

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