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Achilles is asked to race against the tortoise in 5000m run, with the condition that the tortoise is given a head start. Achilles knows that his velocity is 10 times the velocity of tortoise. What can the head start be at most in order that Achilles would win the race???
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Let "u" be the Achilles race speed, in .
Then the tortoise race speed is , according to the condition.
Let "h" will be the value of the tortoise head start, in meters.
Then the tortoise should cover only 5000-h meters.
To win, Achilles time, should be less than the tortoise time :
< , or
5000 < (5000-h)*10, or
5000 < 50000 - 10h ---> 10h < 450000 ---> h < = 4500 m.