Luis had 5 times as many white pens as black pens. After giving away 9 white pens and buying another 23 black pens, he had an equal number of white and black pens. How many white pens did Luis have at first?
| |
White pens |
Black pens |
| Before |
5 u |
1 u |
| Change |
- 9 |
+ 23 |
| After |
5 u - 9 |
1 u + 23 |
The number of white and black pens is the same in the end.
5 u - 9 = 1 u + 23
5 u - 1 u = 23 + 9
4 u = 9 + 23
4 u = 32
1 u = 32 ÷ 4 = 8
Number of white pens that Luis had at first
= 5 u
= 5 x 8
= 40
Answer(s): 40
