Wendy had a collection of 1780 black, silver and grey marbles. After Wendy gave away 300 black marbles, the number of black marbles was 160 fewer than the number of silver marbles. Given that the number of grey marbles was thrice as many as the number of silver marbles, how many black marbles did Wendy have at first?
| |
Black marbles |
Silver marbles |
Grey marbles |
Total |
| Before |
1 u + 300 |
1 u + 160 |
3 u + 480 |
1780 |
| Change |
- 300 |
|
|
|
| After |
1 u |
1 u + 160 |
3 u + 480 |
|
Number of grey marbles in the end
= 3 x (1 u + 160)
= 3 u + 480
Total number of marbles at first
= 1 u + 300 + 1 u + 160 + 3 u + 480
= 5 u + 940
5 u + 940 = 1780
5 u = 1780 - 940
5 u = 840
1 u = 840 ÷ 5 = 168
Number of black marbles that Wendy had at first
= 1 u + 300
= 168 + 300
= 468
Answer(s): 468
