Liam has a total of 29 of grey and white pencils.
15 of the grey pencils and half of the white pencils are new. How many of his white pencils are new if he has a total of 10 new pencils?
| |
Grey pencils |
White pencils |
Total |
| Total |
5 u |
2 p |
29 |
| New |
1 u |
1 p |
10 |
| Old |
4 u |
1 p |
19 |
Number of old pencils
= 29 - 10
= 19
1 u + 1 p = 10 --- (1)
4 u + 1 p = 19 --- (2)
(2) - (1)
(4 u + 1 p) - (1 u + 1 p) = 19 - 10
4 u - 1 u = 9
3 u = 9
1 u = 9 ÷ 3 = 3
Number of new white pencils
= 10 - 1 u
= 10 - 3
= 7
Answer(s): 7
