The average number of playing cards George and Peter had was 443. The average number of playing cards George and Pierre had was 248. If the ratio of Peter's playing cards to Pierre's playing cards was 7 : 2, find the number of playing cards George had.
Total number of cards that George and Peter had
= 2 x 443
= 886

Total number of cards that George and Pierre had
= 2 x 248
= 496

Number of playing cards Peter had = 7 u
Number of playing cards Pierre had = 2 u

George's cards + 7 u = 886 --- (1)
George's cards + 2 u = 496 --- (2)

(1) - (2)
7 u - 2 u = 886 - 496
5 u = 390
1 u = 390 ÷ 5 = 78

Number of playing cards that Pierre had
= 2 u
= 2 x 78
= 156

Number of playing cards that George had
= 496 - 156
= 340

Answer(s): 340