The ratio of the number of red buttons to green buttons is 7 : 2. After Jack gives away 70 red buttons and buys another 90 green buttons, there is equal number of red buttons and green buttons. How many buttons does Jack have now?
| |
Red |
Green |
| Before |
7 u |
2 u |
| Change |
- 70 |
+ 90 |
| After |
7 u - 70 |
2 u + 90 |
The number of red buttons and green buttons in the end is the same.
7 u - 70 = 2 u + 90
7 u - 2 u = 90 + 70
5 u = 160
1 u = 160 ÷ 5 = 32
Number of buttons that Jack has now
= 7 u - 70 + 2 u + 90
= 7 u + 2 u - 70 + 90
= 9 u + 20
= 9 x 32 + 20
= 288 + 20
= 308
Answer(s): 308
