Jeremiah, Dylan, Jackson and Nora share the same hobby of collecting erasers. The average number of erasers collected by the 4 friends is 25. Dylan collected 7 more erasers than Jackson but 14 fewer erasers than Jeremiah. Nora collected 4 erasers fewer than Jackson. Find the average number of erasers collected by Dylan and Nora. Round off your answer to the nearest whole number.
Number of erasers Jackson collected = 1 u
Number of erasers Dylan collected = 1 u + 7
Number of erasers Jeremiah collected = 1 u + 7 + 14 = 1 u + 21
Number of erasers Nora collected = 1 u - 4

Total number of erasers collected
= 4 x 25
= 100

Total number of erasers collected in units
= 1 u + 1 u + 7 + 1 u + 21 + 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 Dylan and Nora
= 1 u + 7 + 1 u - 4
= 2 u + 3
= 2 x 19 + 3
= 41

Average number of erasers collected by Dylan and Nora
= 41 ÷ 2
≈ 21 (Round off to the nearest whole number.)

Answer(s): 21