Olivia had a collection of 2350 black, grey and yellow balls. After Olivia gave away 270 black balls, the number of black balls was 170 fewer than the number of grey balls. Given that the number of yellow balls was thrice as many as the number of grey balls, how many black balls did Olivia have at first?
| |
Black balls |
Grey balls |
Yellow balls |
Total |
| Before |
1 u + 270 |
1 u + 170 |
3 u + 510 |
2350 |
| Change |
- 270 |
|
|
|
| After |
1 u |
1 u + 170 |
3 u + 510 |
|
Number of yellow balls in the end
= 3 x (1 u + 170)
= 3 u + 510
Total number of balls at first
= 1 u + 270 + 1 u + 170 + 3 u + 510
= 5 u + 950
5 u + 950 = 2350
5 u = 2350 - 950
5 u = 1400
1 u = 1400 ÷ 5 = 280
Number of black balls that Olivia had at first
= 1 u + 270
= 280 + 270
= 550
Answer(s): 550
