Opal had five times the number of wooden blocks as Ben. Opal used all her blocks to build 10 identical houses. Ben used all his blocks to build 4 identical houses. Opal used 9 more blocks than Ben for each house. How many blocks did Ben have?

	Opal	Ben
Number	10	4
Value	1 u + 9	1 u
Total value	10 u + 90	4 u

Number of wooden blocks that Ben used for each house = 1 u
Number of wooden blocks that Opal used for each house = 1 u + 9

Number of wooden blocks that Ben had
= 4 x 1 u
= 4 u

Number of wooden blocks that Opal had
= 10 x (1 u + 9)
= 10 u + 90

Opal had five times the number of wooden blocks as Ben.

5 x 4 u = 10 u + 90
20 u = 10 u + 90
20 u - 10 u = 90
10 u = 90

1 u = 90 ÷ 10 = 9

Number of blocks that Ben had
= 4 u
= 4 x 9
= 36

Answer(s): 36