Salik, Andrew, Maya and Samuel share the same hobby of collecting stamps. The average number of stamps collected by the 4 friends is 20. Andrew collected 6 more stamps than Maya but 13 fewer stamps than Salik. Samuel collected 5 stamps fewer than Maya. Find the average number of stamps collected by Andrew and Samuel. Round off your answer to the nearest whole number.
Number of stamps Maya collected = 1 u
Number of stamps Andrew collected = 1 u + 6
Number of stamps Salik collected = 1 u + 6 + 13 = 1 u + 19
Number of stamps Samuel collected = 1 u - 5

Total number of stamps collected
= 4 x 20
= 80

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

4 u + 20 = 80
4 u = 80 - 20 = 60

1 u = 60 ÷ 4 = 15

Total number of stamps collected by Andrew and Samuel
= 1 u + 6 + 1 u - 5
= 2 u + 1
= 2 x 15 + 1
= 31

Average number of stamps collected by Andrew and Samuel
= 31 ÷ 2
≈ 16 (Round off to the nearest whole number.)

Answer(s): 16