Multiple choice

A man travels from Town A to Town B at 60 km/h and returns at 100 km/h. Find his average speed for the two-way journey.

  1. 65

  2. 75

  3. 80

  4. 85

  5. 37.5
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Average speed for a round trip with speeds v1 and v2 is (2 * v1 * v2) / (v1 + v2). Here, (2 * 60 * 100) / (60 + 100) = 12000 / 160 = 75 km/h.

AI explanation

When equal distances are traveled at two different speeds, the average speed is calculated using the harmonic mean formula: 2xy divided by (x + y). Substituting the speeds 60 km/h and 100 km/h gives 2 times 60 times 100 divided by 160. This equals 12000 divided by 160, resulting in an average speed of 75 km/h.

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