The ratio of the number of blue marbles to green marbles is 7 : 4. After Will gives away 10 blue marbles and buys another 20 green marbles, there is equal number of blue marbles and green marbles. How many marbles does Will have now?
| |
Blue |
Green |
| Before |
7 u |
4 u |
| Change |
- 10 |
+ 20 |
| After |
7 u - 10 |
4 u + 20 |
The number of blue marbles and green marbles in the end is the same.
7 u - 10 = 4 u + 20
7 u - 4 u = 20 + 10
3 u = 30
1 u = 30 ÷ 3 = 10
Number of marbles that Will has now
= 7 u - 10 + 4 u + 20
= 7 u + 4 u - 10 + 20
= 11 u + 10
= 11 x 10 + 10
= 110 + 10
= 120
Answer(s): 120
