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Jill arranges quarters in stacks of increasing powers of 2, starting with the zeroth power (20). If she ends up with six stacks, how many coins has she used?

1 Answer

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Stack 1 : 2^0 = 1 quarter.
Stack 2 : 2^1 = 2 quarters.
Stack 3: 2^2 = 4 quarters.
Stack 4: 2^3 = 8 quarters.
Stack 5 : 2^4 = 16 quarters.
Stack 6: 2^5 = 32 quarters.
1 + 2 + 4 + 8 + 16 + 32 = 63
Answer: She used 63 quarters.
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