The littlesister as a flag

Martins littlesister has been hung up in a flagpole, can you find the height of the flagpole ?

Martin stands 15 meters from the flagpole. Between Martin and the flagpole stands a 7,5 meters high hedge and he can just see the top of the flagpole. Martin stands 5 meter from the hedge and his height is 1m 80 cm.

Martin is pulling his little sister down in a rate of 42,5 % per minut. How many minuttes will it take to get the little sister 0,5 meters from the ground?

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