Jeremy had 4 times as many black notebooks as blue notebooks. After giving away 3 black notebooks and buying another 6 blue notebooks, he had an equal number of black and blue notebooks. How many black notebooks did Jeremy have at first?
| |
Black notebooks |
Blue notebooks |
| Before |
4 u |
1 u |
| Change |
- 3 |
+ 6 |
| After |
4 u - 3 |
1 u + 6 |
The number of black and blue notebooks is the same in the end.
4 u - 3 = 1 u + 6
4 u - 1 u = 6 + 3
3 u = 3 + 6
3 u = 9
1 u = 9 ÷ 3 = 3
Number of black notebooks that Jeremy had at first
= 4 u
= 4 x 3
= 12
Answer(s): 12
