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Justin and Ari go on a 30 km run. They usually run together at a speed of 10 km/h. If they start together but Justin runs at 12 his usual speed and Ari runs at 112 times her usual speed, how many hours after Ari finishes will Justin finish?

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Answer:

4 hours

Step-by-step explanation:

Distance covered = 30 km

Usual Speed of both = 10km/hr

Justin's speed = 1/2 * 10 = 5km/hr

Ari's speed = 3/2 * 10 = 15 km/hr

Time taken = distance / speed

Justin's time = 30 / 5 = 6 hours

Ari's time = 30 / 15 = 2 hours

Time difference = (6 - 2) = 4 hours

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