Mrs. Johnson is buying clay for her 20 art students. She needs 1 pack of clay for each student. There are 6 packs of clay in each case. How many cases does Mrs. Johnson need to buy to have enough clay for all her students? How many extra packs will she have?

20/6 = 3 1/3 cases needed.

Given that, how many extra packs will she have?

4 extra packs and 4 cases

To find out how many cases Mrs. Johnson needs to buy, divide the total number of clay packs by the number of packs in each case.

First, calculate the total number of packs needed:
Total number of packs = Number of students * Number of packs per student = 20 * 1 = 20

Since there are 6 packs in each case, divide the total number of packs by 6 to find the number of cases:
Number of cases = Total number of packs / Packs per case = 20 / 6 = 3 with a remainder of 2.

Mrs. Johnson needs to buy 3 full cases to have enough clay for all her students. Additionally, she will have 2 extra packs.