Tommy, Aria, Hannah and Stella share the same hobby of collecting coins. The average number of coins collected by the 4 friends is 20. Aria collected 9 more coins than Hannah but 16 fewer coins than Tommy. Stella collected 2 coins fewer than Hannah. Find the average number of coins collected by Aria, Hannah and Stella. Round off your answer to the nearest whole number.
Number of coins Hannah collected = 1 u
Number of coins Aria collected = 1 u + 9
Number of coins Tommy collected = 1 u + 9 + 16 = 1 u + 25
Number of coins Stella collected = 1 u - 2

Total number of coins collected
= 4 x 20
= 80

Total number of coins collected in units
= 1 u + 1 u + 9 + 1 u + 25 + 1 u - 2
= 4 u + 32

4 u + 32 = 80
4 u = 80 - 32 = 48

1 u = 48 ÷ 4 = 12

Total number of coins collected by Aria, Hannah and Stella
= 1 u + 9 + 1 u + 1 u - 2
= 3 u + 7
= 3 x 12 + 7
= 43

Average number of coins collected by Aria, Hannah and Stella
= 43 ÷ 3
≈ 14 (Round off to the nearest whole number.)

Answer(s): 14