Matthew, Emma, Julian and Hannah share the same hobby of collecting stamps. The average number of stamps collected by the 4 friends is 27. Emma collected 6 more stamps than Julian but 13 fewer stamps than Matthew. Hannah collected 5 stamps fewer than Julian. Find the average number of stamps collected by Emma and Hannah. Round off your answer to the nearest whole number.
Number of stamps Julian collected = 1 u
Number of stamps Emma collected = 1 u + 6
Number of stamps Matthew collected = 1 u + 6 + 13 = 1 u + 19
Number of stamps Hannah collected = 1 u - 5

Total number of stamps collected
= 4 x 27
= 108

Total number of stamps collected in units
= 1 u + 1 u + 6 + 1 u + 19 + 1 u - 5
= 4 u + 20

4 u + 20 = 108
4 u = 108 - 20 = 88

1 u = 88 ÷ 4 = 22

Total number of stamps collected by Emma and Hannah
= 1 u + 6 + 1 u - 5
= 2 u + 1
= 2 x 22 + 1
= 45

Average number of stamps collected by Emma and Hannah
= 45 ÷ 2
≈ 23 (Round off to the nearest whole number.)

Answer(s): 23