Question

Jill arranges quarters in stacks of increasing powers of 2,starting with the zeroth power (2^0).If she ends up with six stacks,how man coins has she used?

Answer 1

2⁰ =  1
2¹ =  2
2² =  4
2³ =  8
2⁴ = 16
2⁵ = 32

The sum  =  (the next power of 2) - 1

                     2⁶ - 1  =  63 .

                               ($15.75 if she's stacking quarters)