The ratio of the number of blue cards to green cards is 9 : 7. After Ken gives away 70 blue cards and buys another 80 green cards, there is equal number of blue cards and green cards. How many cards does Ken have now?
| |
Blue |
Green |
| Before |
9 u |
7 u |
| Change |
- 70 |
+ 80 |
| After |
9 u - 70 |
7 u + 80 |
The number of blue cards and green cards in the end is the same.
9 u - 70 = 7 u + 80
9 u - 7 u = 80 + 70
2 u = 150
1 u = 150 ÷ 2 = 75
Number of cards that Ken has now
= 9 u - 70 + 7 u + 80
= 9 u + 7 u - 70 + 80
= 16 u + 10
= 16 x 75 + 10
= 1200 + 10
= 1210
Answer(s): 1210
