Stella, Harper, Noah and Sophia share the same hobby of collecting erasers. The average number of erasers collected by the 4 friends is 23. Harper collected 8 more erasers than Noah but 15 fewer erasers than Stella. Sophia collected 3 erasers fewer than Noah. Find the average number of erasers collected by Harper, Noah and Sophia. Round off your answer to the nearest whole number.
Number of erasers Noah collected = 1 u
Number of erasers Harper collected = 1 u + 8
Number of erasers Stella collected = 1 u + 8 + 15 = 1 u + 23
Number of erasers Sophia collected = 1 u - 3

Total number of erasers collected
= 4 x 23
= 92

Total number of erasers collected in units
= 1 u + 1 u + 8 + 1 u + 23 + 1 u - 3
= 4 u + 28

4 u + 28 = 92
4 u = 92 - 28 = 64

1 u = 64 ÷ 4 = 16

Total number of erasers collected by Harper, Noah and Sophia
= 1 u + 8 + 1 u + 1 u - 3
= 3 u + 5
= 3 x 16 + 5
= 53

Average number of erasers collected by Harper, Noah and Sophia
= 53 ÷ 3
≈ 18 (Round off to the nearest whole number.)

Answer(s): 18