Matthew made a fruit salad, in which the ratio of blueberries to red grapes is 8: 6. if matthew used 28 blueberries, how many red grapes did he use? [type your answer as a number.]

This relationship is proportional and you can write it out as 8/6 = 28/?. The simplest way to find the missing value is to simply 8/6 to 4/3. We now have 4/3 = 28/?. Four times seven is twenty eight. Multiply the denominator by seven because you must multiply both sides by the same value to find that the missing value is equal to 21.

Basically, 21 red grapes.