Kylie had a collection of 2220 black, red and white marbles. After Kylie gave away 310 black marbles, the number of black marbles was 230 fewer than the number of red marbles. Given that the number of white marbles was twice as many as the number of red marbles, how many black marbles did Kylie have at first?
| |
Black marbles |
Red marbles |
White marbles |
Total |
| Before |
1 u + 310 |
1 u + 230 |
2 u + 460 |
2220 |
| Change |
- 310 |
|
|
|
| After |
1 u |
1 u + 230 |
2 u + 460 |
|
Number of white marbles in the end
= 2 x (1 u + 230)
= 2 u + 460
Total number of marbles at first
= 1 u + 310 + 1 u + 230 + 2 u + 460
= 4 u + 1000
4 u + 1000 = 2220
4 u = 2220 - 1000
4 u = 1220
1 u = 1220 ÷ 4 = 305
Number of black marbles that Kylie had at first
= 1 u + 310
= 305 + 310
= 615
Answer(s): 615
