The ratio of the number of blue cards to red cards is 9 : 4. After Ethan gives away 30 blue cards and buys another 80 red cards, there is equal number of blue cards and red cards. How many cards does Ethan have now?
| |
Blue |
Red |
| Before |
9 u |
4 u |
| Change |
- 30 |
+ 80 |
| After |
9 u - 30 |
4 u + 80 |
The number of blue cards and red cards in the end is the same.
9 u - 30 = 4 u + 80
9 u - 4 u = 80 + 30
5 u = 110
1 u = 110 ÷ 5 = 22
Number of cards that Ethan has now
= 9 u - 30 + 4 u + 80
= 9 u + 4 u - 30 + 80
= 13 u + 50
= 13 x 22 + 50
= 286 + 50
= 336
Answer(s): 336
