Harris, Nora, Harper and Dylan share the same hobby of collecting buttons. The average number of buttons collected by the 4 friends is 30. Nora collected 7 more buttons than Harper but 16 fewer buttons than Harris. Dylan collected 2 buttons fewer than Harper. Find the average number of buttons collected by Nora and Dylan. Round off your answer to the nearest whole number.
Number of buttons Harper collected = 1 u
Number of buttons Nora collected = 1 u + 7
Number of buttons Harris collected = 1 u + 7 + 16 = 1 u + 23
Number of buttons Dylan collected = 1 u - 2

Total number of buttons collected
= 4 x 30
= 120

Total number of buttons collected in units
= 1 u + 1 u + 7 + 1 u + 23 + 1 u - 2
= 4 u + 28

4 u + 28 = 120
4 u = 120 - 28 = 92

1 u = 92 ÷ 4 = 23

Total number of buttons collected by Nora and Dylan
= 1 u + 7 + 1 u - 2
= 2 u + 5
= 2 x 23 + 5
= 51

Average number of buttons collected by Nora and Dylan
= 51 ÷ 2
≈ 26 (Round off to the nearest whole number.)

Answer(s): 26