The average number of playing cards Daniel and Julian had was 451. The average number of playing cards Daniel and Jeremy had was 250. If the ratio of Julian's playing cards to Jeremy's playing cards was 5 : 2, find the number of playing cards Daniel had.
Total number of cards that Daniel and Julian had
= 2 x 451
= 902

Total number of cards that Daniel and Jeremy had
= 2 x 250
= 500

Number of playing cards Julian had = 5 u
Number of playing cards Jeremy had = 2 u

Daniel's cards + 5 u = 902 --- (1)
Daniel's cards + 2 u = 500 --- (2)

(1) - (2)
5 u - 2 u = 902 - 500
3 u = 402
1 u = 402 ÷ 3 = 134

Number of playing cards that Jeremy had
= 2 u
= 2 x 134
= 268

Number of playing cards that Daniel had
= 500 - 268
= 232

Answer(s): 232