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Grandmas and Trolls - Math Brain Teasers

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Grandmas and Trolls - Math Brain Teasers


You are on your way to visit your Grandma, who lives at the end of the valley.


It's her birthday, and you want to give her the cakes you've made.

Between your house and her house, you have to cross 7 bridges, and as it goes in the land of make believe, there is a troll under every bridge!
Each troll, quite rightly, insists that you pay a troll toll.
Before you can cross their bridge, you have to give them half of the cakes you are carrying, but as they are kind trolls, they each give you back a single cake.
How many cakes do you have to leave home with to make sure that you arrive at Grandma's with exactly 2 cakes?

At each bridge you are required to give half of your cakes (not half of a cake), and you receive one back.
Which leaves you with 2 cakes after every bridge. Answer: 2 - The minimum number of cakes is 2 No matter how many bridges there are. With 2 cakes you have to give one of them away and then will get another as a reward. You can cross further bridges infinitely.

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I dont think this is right but im going to post before looking because its just crazy enough to possibly be right.

I say you need 2 cakes


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