First you have to divide the total number of keys by the parts that the ratio contains: 88/(13+9) = 88/22 = 4 2. This number is how many keys are in 1 part of the ratio so you have to times this number by the number in the ratio to find out how many keys there are in that section: 13 x 4 = 52 (there are 52 white keys) 9 x 4 = 36 (there are 36 black keys) 3. To check your answer, ad up both parts of the ratio! 52+36 = 88 Hope this helps :)
