The ratio of the number of blue cards to red cards is 5 : 2. After Justin gives away 60 blue cards and buys another 90 red cards, there is equal number of blue cards and red cards. How many cards does Justin have now?
| |
Blue |
Red |
| Before |
5 u |
2 u |
| Change |
- 60 |
+ 90 |
| After |
5 u - 60 |
2 u + 90 |
The number of blue cards and red cards in the end is the same.
5 u - 60 = 2 u + 90
5 u - 2 u = 90 + 60
3 u = 150
1 u = 150 ÷ 3 = 50
Number of cards that Justin has now
= 5 u - 60 + 2 u + 90
= 5 u + 2 u - 60 + 90
= 7 u + 30
= 7 x 50 + 30
= 350 + 30
= 380
Answer(s): 380
