How many groups of 2 make four groups of 5?

To find out how many groups of 2 make four groups of 5, first calculate the total number in four groups of 5, which is (4 \times 5 = 20). Then, divide this total by the size of the groups you are forming: (20 \div 2 = 10). Therefore, it takes 10 groups of 2 to make four groups of 5.