Of words. if necessary, use / for the fraction bar.
a chessboard has 64 squares. george places 1 grain of rice on the first square, 2 grains on the second square, 4 grains on the third square, 8 grains on the fourth square, and so on, until he has placed grains of rice on 10 squares.
once george has put rice on the 10th square, he has placed a total of
grains of rice on the chess board.