The average number of playing cards Rael and Pierre had was 440. The average number of playing cards Rael and Charlie had was 237. If the ratio of Pierre's playing cards to Charlie's playing cards was 9 : 2, find the number of playing cards Rael had.
Total number of cards that Rael and Pierre had
= 2 x 440
= 880

Total number of cards that Rael and Charlie had
= 2 x 237
= 474

Number of playing cards Pierre had = 9 u
Number of playing cards Charlie had = 2 u

Rael's cards + 9 u = 880 --- (1)
Rael's cards + 2 u = 474 --- (2)

(1) - (2)
9 u - 2 u = 880 - 474
7 u = 406
1 u = 406 ÷ 7 = 58

Number of playing cards that Charlie had
= 2 u
= 2 x 58
= 116

Number of playing cards that Rael had
= 474 - 116
= 358

Answer(s): 358