Answer:
187.5 doughnuts (about 188)
62.5 candy bars (about 63)
Step-by-step explanation:
So the proportion of middle schoolers who prefer doughnuts is p = 9/12. That means the proportion of middle schoolers who prefer candy is 1 - 9/12 = 3/12.
The number of middle schoolers is n = 250.
Let X represent the number of doughnuts you need. The expected number is E(X) = np, so multiply them together:
E(X) = np
E(X) = 250 * 9/12 = 187.5 doughnuts
Let Y represent the number of candy bars you need. The expected number is E(Y) = np, so multiply them together:
E(Y) = np
E(Y) = 250 * 3/12 = 62.5 candy bars