The average number of playing cards Riordan and Andy had was 442. The average number of playing cards Riordan and Bobby had was 223. If the ratio of Andy's playing cards to Bobby's playing cards was 5 : 2, find the number of playing cards Riordan had.
Total number of cards that Riordan and Andy had
= 2 x 442
= 884

Total number of cards that Riordan and Bobby had
= 2 x 223
= 446

Number of playing cards Andy had = 5 u
Number of playing cards Bobby had = 2 u

Riordan's cards + 5 u = 884 --- (1)
Riordan's cards + 2 u = 446 --- (2)

(1) - (2)
5 u - 2 u = 884 - 446
3 u = 438
1 u = 438 ÷ 3 = 146

Number of playing cards that Bobby had
= 2 u
= 2 x 146
= 292

Number of playing cards that Riordan had
= 446 - 292
= 154

Answer(s): 154