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DrPengin

The Greed Bridge

Question

One day, a man is standing by a river thinking of ways to make money fast. The devil appears in front of him and offers him a deal: every time he crosses the bridge, the money in his pocket doubles. But after the money is doubled, the man must pay a charge of $24. One cross means from one side of the river to the other, not back and forth. The man crosses 3 times. After the 3rd time of paying the charge, the man looks in his pocket to find $0. How much did he have in the beginning?

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Answer...

 

Spoiler

21$

First trip-- 21x2=42  42-24=18

Second trip-- 18x2=36  36-24=12

Third trip-- 12x2=24  24-24=0

I wouldn't do the deal with anything less than $24.01 in my pocket.

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Spoiler

Begin with x.

First crossing and fee: 2(x-$12)
Second crossing and fee: 4(x-$18)
Third crossing and fee: 8(x-$21) = 0.

x=$21

 

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