The average number of playing cards Daniel and Cole had was 448. The average number of playing cards Daniel and Albert had was 228. If the ratio of Cole's playing cards to Albert's playing cards was 9 : 4, find the number of playing cards Daniel had.
Total number of cards that Daniel and Cole had
= 2 x 448
= 896

Total number of cards that Daniel and Albert had
= 2 x 228
= 456

Number of playing cards Cole had = 9 u
Number of playing cards Albert had = 4 u

Daniel's cards + 9 u = 896 --- (1)
Daniel's cards + 4 u = 456 --- (2)

(1) - (2)
9 u - 4 u = 896 - 456
5 u = 440
1 u = 440 ÷ 5 = 88

Number of playing cards that Albert had
= 4 u
= 4 x 88
= 352

Number of playing cards that Daniel had
= 456 - 352
= 104

Answer(s): 104