A man covers a distance of 20 km in 3.5 hours partly by running and partly by walking. If he walks at 4 kmph and runs at 10 kmph, find the distance he covers by walking.
Correct answer: A. 10 km
- A. 10 km
- B. 8 km
- C. 12 km
- D. 9 km
Explanation
Let the walking distance be x km, so the running distance is (20 - x) km. Then x/4 hours + (20 - x)/10 hours = 3.5 hours, giving 5x + 40 - 2x = 70 and x = 10 km. A student may choose 8 km by reversing the walking and running distances or using an arithmetic rather than time equation.
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