Peter has a total of 37 of purple and gold notebooks.
13 of the purple notebooks and half of the gold notebooks are new. How many of his gold notebooks are new if he has a total of 16 new notebooks?
| |
Purple notebooks |
Gold notebooks |
Total |
| Total |
3 u |
2 p |
37 |
| New |
1 u |
1 p |
16 |
| Old |
2 u |
1 p |
21 |
Number of old notebooks
= 37 - 16
= 21
1 u + 1 p = 16 --- (1)
2 u + 1 p = 21 --- (2)
(2) - (1)
(2 u + 1 p) - (1 u + 1 p) = 21 - 16
2 u - 1 u = 5
1 u = 5
1 u = 5 ÷ 1 = 5
Number of new gold notebooks
= 16 - 1 u
= 16 - 5
= 11
Answer(s): 11
