Question

DIRECTION for the question: Solve the following question and mark the best possible option. A car travels 39 km in 45 minutes at speed \(x\) km/h for the first 15 minutes, then at double speed for the next 20 minutes and again at the original speed for the remaining time. Find \(x\).

• A. 31.2
• B. 36
• C. 40
• D. 52
• E. 39

Hint:

Convert minutes to hours when solving speed–distance problems.

Answer 1

The Correct Option is B

Convert minutes to hours. First 15 minutes: \[ \frac{15}{60}x = 0.25x \] Next 20 minutes at double speed: \[ \frac{20}{60}(2x) = \frac{40x}{60} = \frac{2x}{3} \] Remaining 10 minutes: \[ \frac{10}{60}x = \frac{x}{6} \] Total distance: \[ 0.25x + \frac{2x}{3} + \frac{x}{6} = 39 \] \[ \frac{13x}{12} = 39 \] \[ x = 36 \]