Miss.Muffet males a fruit salad by adding 31/2 pounds of grapes and 4 1/4 pounds of apples to every 2 1/4 pounds of melon. How many pounds of grapes does she use in 50 pounds of fruit salad?

The basic recipe makes 3 1/2 + 4 1/4 + 2 1/4 = 10 pounds of fruit salad. 50 pounds is 5 times that much. So, 50 pounds of fruit salad will contain 5 times 3 1/2 pounds of grapes.