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?

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.