A man travels some distance at a speed of 12 km/hr and returns at a speed of 9 km/hr. If the total time taken by him is 2 hrs 20 minutes the distance is

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A man travels some distance at a speed of 12 km/hr and returns at a speed of 9 km/hr. If the total time taken by him is 2 hrs 20 minutes the distance is

A35 km

B21 km.

C9 km

D12 km

Answer:

D. 12 km

Read Explanation:

2 hr 20 min = 2 + 1/3 = 7/3 hr Let the total distance be x km. x/12 + x/9 = 7/3 ⇒ (4x + 3x)36 = 7/3 ⇒ 7x/36 = 7/3 ⇒ x = 7/3 × (36/7) x = 12 OR Total distance covered = 2xy/(x + y) × time = 2 × 12 × 9/(21) × 7/3 = 1512/63 = 24 Distance = 24/2 = 12

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