A car travels a distance of 240 km at a uniform speed. If the speed is reduced by 10 km/h, it takes 2 hours longer. Find the original speed. MCQ with Answer and Explanation
A car travels a distance of 240 km at a uniform speed. If the speed is reduced by 10 km/h, it takes 2 hours longer. Find the original speed.
A. 50 km/h
B. 60 km/h
C. 40 km/h
D. 30 km/h
Answer: Option C
Solution (By JKSSB Mock Tests)
Let original speed be s. 240 / (s - 10) - 240 / s = 2 => 120 / (s - 10) - 120 / s = 1 => 1200 = s(s - 10). Solving s^2 - 10s - 1200 = 0 gives (s - 40)(s + 30) = 0. Since speed is positive, s = 40 km/h.
Explanation:
Let speed of stream be s. Downstream speed = 6 + s. Upstream speed = 6 - s. Given: 2 * (6 - s) = 6 + s => 12 - 2s = 6 + s => 3s = 6 => s = 2 km/h.
A commuter drives to his consulting firm at 30 km/h and arrives 15 minutes late. If he increases his speed to 40 km/h, he arrives 5 minutes early. Find the distance to his firm.
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