At Central Middle School the 108 students who take the AMC 8 meet in the evening to talk about problems and eat an average of two cookies apiece. Walter and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of cookies, lists these items:
1 1/2 cups of flour
3 tablespoons butter
3/4 cups sugar
1 package of chocolate drops
They will make only full recipes, no partial recipes.
They learn that a big concert is scheduled for the same night and attendance will be down 25%. How many recipes of cookies should they make for their smaller party?
How many cookies in a pan? There is a number missing.
I'm assuming that "attendance will be down 25%" means:
108 - [ 25% x 108] ==108 - 27 ==81 students attending the concert.
Since each student will eat an average of 2 cookies, then that means:
Walter and Gretel will have to bake: 81 x 2 ==162 cookies. Since their recipe, which make one pan holding 15 cookies, then the number of recipes they will have to make should be:
162 cookies / 15 cookies per one pan ==10.8 pans or recipes. Since they have to make full recipes, then that means they will have to bake a total of 11 recipes for the 81 students attending the concert.
If you wish to calculate the total ingredients needed for the 11 recipes, then you will simply multiply:
11 x 1 1/2 cups of flour ==16.50 cups
11 x 2 eggs ==22 eggs
11 x 3 tabespoons of butter ==33 tablespoons.
11 x 3/4 cups of sugar ==8.25 cups.
11 x 1 package of chocolate drops ==11 packages.