Answer:
Each friend would get 1/7th of a pie.
Explanation:
Jilly started with 4 pies, and her brother ate half of one pie, which means he ate 1/2 of a pie. So, Jilly has 3 and a half pies left, which is equal to 7/2 pies. If she wants to divide the pies equally among her 21 friends, she can divide 7/2 by 21 to find the fraction of the pie that each friend will get:
(7/2) ÷ 21 = 7/2 ÷ 21/1 = 7/2 x 1/21 = 7/42
Therefore, each friend would get 7/42 of a pie, which can be simplified to 1/6 or 1/7 (rounded to the nearest whole number). So, each friend would get 1/7th of a pie.