Zane had 4 times as many black pens as purple pens. After giving away 10 black pens and buying another 17 purple pens, he had an equal number of black and purple pens. How many black pens did Zane have at first?
| |
Black pens |
Purple pens |
| Before |
4 u |
1 u |
| Change |
- 10 |
+ 17 |
| After |
4 u - 10 |
1 u + 17 |
The number of black and purple pens is the same in the end.
4 u - 10 = 1 u + 17
4 u - 1 u = 17 + 10
3 u = 10 + 17
3 u = 27
1 u = 27 ÷ 3 = 9
Number of black pens that Zane had at first
= 4 u
= 4 x 9
= 36
Answer(s): 36
