Oliver, Lily, Henry and Lucas share the same hobby of collecting erasers. The average number of erasers collected by the 4 friends is 25. Lily collected 8 more erasers than Henry but 12 fewer erasers than Oliver. Lucas collected 4 erasers fewer than Henry. Find the average number of erasers collected by Lily, Henry and Lucas. Round off your answer to the nearest whole number.
Number of erasers Henry collected = 1 u
Number of erasers Lily collected = 1 u + 8
Number of erasers Oliver collected = 1 u + 8 + 12 = 1 u + 20
Number of erasers Lucas collected = 1 u - 4

Total number of erasers collected
= 4 x 25
= 100

Total number of erasers collected in units
= 1 u + 1 u + 8 + 1 u + 20 + 1 u - 4
= 4 u + 24

4 u + 24 = 100
4 u = 100 - 24 = 76

1 u = 76 ÷ 4 = 19

Total number of erasers collected by Lily, Henry and Lucas
= 1 u + 8 + 1 u + 1 u - 4
= 3 u + 4
= 3 x 19 + 4
= 61

Average number of erasers collected by Lily, Henry and Lucas
= 61 ÷ 3
≈ 20 (Round off to the nearest whole number.)

Answer(s): 20