Risa had a collection of 2070 brown, white and red balls. After Risa gave away 300 brown balls, the number of brown balls was 220 fewer than the number of white balls. Given that the number of red balls was thrice as many as the number of white balls, how many brown balls did Risa have at first?
| |
Brown balls |
White balls |
Red balls |
Total |
| Before |
1 u + 300 |
1 u + 220 |
3 u + 660 |
2070 |
| Change |
- 300 |
|
|
|
| After |
1 u |
1 u + 220 |
3 u + 660 |
|
Number of red balls in the end
= 3 x (1 u + 220)
= 3 u + 660
Total number of balls at first
= 1 u + 300 + 1 u + 220 + 3 u + 660
= 5 u + 1180
5 u + 1180 = 2070
5 u = 2070 - 1180
5 u = 890
1 u = 890 ÷ 5 = 178
Number of brown balls that Risa had at first
= 1 u + 300
= 178 + 300
= 478
Answer(s): 478
