16Hit1600
AlgebraHardDistance from a round trip at two speeds

Algebra practice question

Sara cycles from home to a park at 12 kilometres per hour and walks back along the same route at 4 kilometres per hour. The whole trip takes 2 hours. How many kilometres is it from home to the park?

Answer: 6

d/12 + d/4 = 2 → d/12 + 3d/12 = 4d/12 = d/3 = 2 → d = 6.

Common wrong answers

If you answered 3
3 comes from d/3 = 2 solved as d = 3, dividing instead of multiplying.
If you answered 16
16 is 2 × 8, using the average of the speeds as if the times were equal.
If you answered 24
24 is 12 × 2, the distance if she cycled the whole time.

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