Multiple choice

A car moves a distance of 200 m. It covers the first half of the distance at speed 40 km/h and the second half of distance at speed v. The average speed is 48 km/h. Find the value of v

  1. 56 km/h

  2. 60 km/h

  3. 50 km/h

  4. 48 km/h
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B Correct answer
Explanation

Average speed = 2 * v1 * v2 / (v1 + v2). 48 = 2 * 40 * v / (40 + v). 24 = 40v / (40 + v). 24(40 + v) = 40v. 960 + 24v = 40v. 16v = 960. v = 60.

AI explanation

Since the car covers equal distances at two different speeds, we use the harmonic mean formula for average speed: (2 * S1 * S2) divided by (S1 + S2). Here, the average speed is 48, the first speed is 40, and the second speed is v. Setting up the equation, 48 equals (2 * 40 * v) divided by (40 + v), which simplifies to 48 * (40 + v) = 80v. Solving this yields 1920 + 48v = 80v, meaning 32v equals 1920, so v is 60 km/h.

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