Samuel, Gabriel, Isabella and Matthew share the same hobby of collecting erasers. The average number of erasers collected by the 4 friends is 30. Gabriel collected 9 more erasers than Isabella but 16 fewer erasers than Samuel. Matthew collected 2 erasers fewer than Isabella. Find the average number of erasers collected by Gabriel, Isabella and Matthew. Round off your answer to the nearest whole number.
Number of erasers Isabella collected = 1 u
Number of erasers Gabriel collected = 1 u + 9
Number of erasers Samuel collected = 1 u + 9 + 16 = 1 u + 25
Number of erasers Matthew collected = 1 u - 2

Total number of erasers collected
= 4 x 30
= 120

Total number of erasers collected in units
= 1 u + 1 u + 9 + 1 u + 25 + 1 u - 2
= 4 u + 32

4 u + 32 = 120
4 u = 120 - 32 = 88

1 u = 88 ÷ 4 = 22

Total number of erasers collected by Gabriel, Isabella and Matthew
= 1 u + 9 + 1 u + 1 u - 2
= 3 u + 7
= 3 x 22 + 7
= 73

Average number of erasers collected by Gabriel, Isabella and Matthew
= 73 ÷ 3
≈ 24 (Round off to the nearest whole number.)

Answer(s): 24