1500. Summing infinite geometric series

1/2 + 1/4 + 1/8 + 1/16 + ... = 1

 1/3 + 1/9 + 1/27 + 1/81 + ... = 1/2

 1/4 + 1/16 + 1/64 + 1/256 + ... = 1/3