A trader drives from Lahore to a nearby town at 60 km/h. At what speed must he return along the same road so that his average speed for the round trip is 72 km/h?
Correct answer C. 90 km/h
Explanation
Using 2 × 60 × x / (60 + x) = 72: 120x = 4320 + 72x, so 48x = 4320 and x = 90 km/h.
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