Ellie, Aria, Aubrey and Dylan share the same hobby of collecting beads. The average number of beads collected by the 4 friends is 24. Aria collected 9 more beads than Aubrey but 12 fewer beads than Ellie. Dylan collected 2 beads fewer than Aubrey. Find the average number of beads collected by Aria and Dylan. Round off your answer to the nearest whole number.
Number of beads Aubrey collected = 1 u
Number of beads Aria collected = 1 u + 9
Number of beads Ellie collected = 1 u + 9 + 12 = 1 u + 21
Number of beads Dylan collected = 1 u - 2

Total number of beads collected
= 4 x 24
= 96

Total number of beads collected in units
= 1 u + 1 u + 9 + 1 u + 21 + 1 u - 2
= 4 u + 28

4 u + 28 = 96
4 u = 96 - 28 = 68

1 u = 68 ÷ 4 = 17

Total number of beads collected by Aria and Dylan
= 1 u + 9 + 1 u - 2
= 2 u + 7
= 2 x 17 + 7
= 41

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

Answer(s): 21