Luke, Rachel, Bryan and Avery share the same hobby of collecting marbles. The average number of marbles collected by the 4 friends is 27. Rachel collected 7 more marbles than Bryan but 14 fewer marbles than Luke. Avery collected 4 marbles fewer than Bryan. Find the average number of marbles collected by Rachel and Avery. Round off your answer to the nearest whole number.
Number of marbles Bryan collected = 1 u
Number of marbles Rachel collected = 1 u + 7
Number of marbles Luke collected = 1 u + 7 + 14 = 1 u + 21
Number of marbles Avery collected = 1 u - 4

Total number of marbles collected
= 4 x 27
= 108

Total number of marbles collected in units
= 1 u + 1 u + 7 + 1 u + 21 + 1 u - 4
= 4 u + 24

4 u + 24 = 108
4 u = 108 - 24 = 84

1 u = 84 ÷ 4 = 21

Total number of marbles collected by Rachel and Avery
= 1 u + 7 + 1 u - 4
= 2 u + 3
= 2 x 21 + 3
= 45

Average number of marbles collected by Rachel and Avery
= 45 ÷ 2
≈ 23 (Round off to the nearest whole number.)

Answer(s): 23