If 13 is 40 percent of a number, we can rewrite this to say 13 = 0.4x, where x is that "some number." 0.4 is just 40 percent, since it is "40 parts out of 100 parts." Dividing each side by 4, we get 13/4 = 0.1x. Multiplying each side by 10, we get 130/4 = x. Dividing 130 by 4, we get 32.5 as our