The ratio of the number of blue cards to red cards is 9 : 4. After Tim gives away 40 blue cards and buys another 50 red cards, there is equal number of blue cards and red cards. How many cards does Tim have now?
| |
Blue |
Red |
| Before |
9 u |
4 u |
| Change |
- 40 |
+ 50 |
| After |
9 u - 40 |
4 u + 50 |
The number of blue cards and red cards in the end is the same.
9 u - 40 = 4 u + 50
9 u - 4 u = 50 + 40
5 u = 90
1 u = 90 ÷ 5 = 18
Number of cards that Tim has now
= 9 u - 40 + 4 u + 50
= 9 u + 4 u - 40 + 50
= 13 u + 10
= 13 x 18 + 10
= 234 + 10
= 244
Answer(s): 244
