A motor cycle covers 40 km with a speed of 20 kph.Find the speed of the motor cycle for the next 40km journey so that the average speed of the whole journey will be 30 kph.
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Answer:
SPEED TIME DISTANCE
First part 20 40%2F20 40
Next part r 40%2Fr 40
Total 40%2F20%2B40%2Fr 80
Average speed wanted 30 kilometer per hour.
80%2F%2840%2F20%2B40%2Fr%29=30
Simplify and solve this for r.
8%2F%282%2B40%2Fr%29=3
8=3%282%2B40%2Fr%29
4=3%281%2B20%2Fr%29
4=3%2B60%2Fr
4r=3r%2B60
highlight%28r=60%29
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