Ivan has a total of 39 of white and silver pens.
15 of the white pens and half of the silver pens are new. How many of his silver pens are new if he has a total of 9 new pens?
| |
White pens |
Silver pens |
Total |
| Total |
5 u |
2 p |
39 |
| New |
1 u |
1 p |
9 |
| Old |
4 u |
1 p |
30 |
Number of old pens
= 39 - 9
= 30
1 u + 1 p = 9 --- (1)
4 u + 1 p = 30 --- (2)
(2) - (1)
(4 u + 1 p) - (1 u + 1 p) = 30 - 9
4 u - 1 u = 21
3 u = 21
1 u = 21 ÷ 3 = 7
Number of new silver pens
= 9 - 1 u
= 9 - 7
= 2
Answer(s): 2
