Natalie had a collection of 1970 brown, gold and black balls. After Natalie gave away 280 brown balls, the number of brown balls was 210 fewer than the number of gold balls. Given that the number of black balls was twice as many as the number of gold balls, how many brown balls did Natalie have at first?
| |
Brown balls |
Gold balls |
Black balls |
Total |
| Before |
1 u + 280 |
1 u + 210 |
2 u + 420 |
1970 |
| Change |
- 280 |
|
|
|
| After |
1 u |
1 u + 210 |
2 u + 420 |
|
Number of black balls in the end
= 2 x (1 u + 210)
= 2 u + 420
Total number of balls at first
= 1 u + 280 + 1 u + 210 + 2 u + 420
= 4 u + 910
4 u + 910 = 1970
4 u = 1970 - 910
4 u = 1060
1 u = 1060 ÷ 4 = 265
Number of brown balls that Natalie had at first
= 1 u + 280
= 265 + 280
= 545
Answer(s): 545
