The average number of playing cards Gabriel and Bobby had was 428. The average number of playing cards Gabriel and Oscar had was 245. If the ratio of Bobby's playing cards to Oscar's playing cards was 5 : 2, find the number of playing cards Gabriel had.
Total number of cards that Gabriel and Bobby had
= 2 x 428
= 856

Total number of cards that Gabriel and Oscar had
= 2 x 245
= 490

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

Gabriel's cards + 5 u = 856 --- (1)
Gabriel's cards + 2 u = 490 --- (2)

(1) - (2)
5 u - 2 u = 856 - 490
3 u = 366
1 u = 366 ÷ 3 = 122

Number of playing cards that Oscar had
= 2 u
= 2 x 122
= 244

Number of playing cards that Gabriel had
= 490 - 244
= 246

Answer(s): 246