There was an equal number of white and black marbles in a packet at first. After 18 black marbles were taken out and 42 white marbles were added into the packet, there was
15 as many black marbles as white marbles. Find the number of black marbles in the packet at first.
| |
White marbles |
Black marbles |
| Before |
5 u - 42 |
1 u + 18 |
| Change |
+ 42 |
- 18 |
| After |
5 u |
1 u |
The number of white and black marbles in the packet is the same at first.
5 u - 42 = 1 u + 18
5 u - 1 u = 18 + 42
4 u = 60
1 u = 60 ÷ 4 = 15
Number of black marbles at first
= 1 u + 18
= 15 + 18
= 33
Answer(s)33
