Miguel asked Sandra to make 90 cookies for his party. Sandra needs ¼ cup of sugar to make 15 cookies. She incorrectly calculated the amount of sugar she will need.
Write a brief note to Sandra describing her mistake and explain to her how to correctly

Sandra's work:
Amount of sugar for 1 cookie: 15 x 1/4c = 15/4 = 3.75 C
Amount of sugar for 90 cookies: 3.75 C x 90 = 337.5 C