Tom has a total of 66 of pink and grey pencils.
16 of the pink pencils and half of the grey pencils are new. How many of his grey pencils are new if he has a total of 15 new pencils?
|
Pink pencils |
Grey pencils |
Total |
Total |
6 u |
2 p |
66 |
New |
1 u |
1 p |
15 |
Old |
5 u |
1 p |
51 |
Number of old pencils
= 66 - 15
= 51
1 u + 1 p = 15 --- (1)
5 u + 1 p = 51 --- (2)
(2) - (1)
(5 u + 1 p) - (1 u + 1 p) = 51 - 15
5 u - 1 u = 36
4 u = 36
1 u = 36 ÷ 4 = 9
Number of new grey pencils
= 15 - 1 u
= 15 - 9
= 6
Answer(s): 6