Harris, Jamie, Jack and Isaac share the same hobby of collecting marbles. The average number of marbles collected by the 4 friends is 23. Jamie collected 6 more marbles than Jack but 17 fewer marbles than Harris. Isaac collected 5 marbles fewer than Jack. Find the average number of marbles collected by Jamie, Jack and Isaac. Round off your answer to the nearest whole number.
Number of marbles Jack collected = 1 u
Number of marbles Jamie collected = 1 u + 6
Number of marbles Harris collected = 1 u + 6 + 17 = 1 u + 23
Number of marbles Isaac collected = 1 u - 5

Total number of marbles collected
= 4 x 23
= 92

Total number of marbles collected in units
= 1 u + 1 u + 6 + 1 u + 23 + 1 u - 5
= 4 u + 24

4 u + 24 = 92
4 u = 92 - 24 = 68

1 u = 68 ÷ 4 = 17

Total number of marbles collected by Jamie, Jack and Isaac
= 1 u + 6 + 1 u + 1 u - 5
= 3 u + 1
= 3 x 17 + 1
= 52

Average number of marbles collected by Jamie, Jack and Isaac
= 52 ÷ 3
≈ 17 (Round off to the nearest whole number.)

Answer(s): 17