Emily, Grace, Nathan and Matthew share the same hobby of collecting pens. The average number of pens collected by the 4 friends is 25. Grace collected 6 more pens than Nathan but 18 fewer pens than Emily. Matthew collected 2 pens fewer than Nathan. Find the average number of pens collected by Grace, Nathan and Matthew. Round off your answer to the nearest whole number.
Number of pens Nathan collected = 1 u
Number of pens Grace collected = 1 u + 6
Number of pens Emily collected = 1 u + 6 + 18 = 1 u + 24
Number of pens Matthew collected = 1 u - 2

Total number of pens collected
= 4 x 25
= 100

Total number of pens collected in units
= 1 u + 1 u + 6 + 1 u + 24 + 1 u - 2
= 4 u + 28

4 u + 28 = 100
4 u = 100 - 28 = 72

1 u = 72 ÷ 4 = 18

Total number of pens collected by Grace, Nathan and Matthew
= 1 u + 6 + 1 u + 1 u - 2
= 3 u + 4
= 3 x 18 + 4
= 58

Average number of pens collected by Grace, Nathan and Matthew
= 58 ÷ 3
≈ 19 (Round off to the nearest whole number.)

Answer(s): 19