Zeph and Archie had 81 pens together. Zeph had 15 more pens than Archie. Both of them sold some of their pens. Archie sold 20% less pens than what Zeph sold. In the end, Archie had half as many pens left as Zeph. How many pens had Zeph left?
| |
Zeph
(1) |
Archie
(2) |
Make p the same
(2)x2 = (3) |
Comparing Zeph
and Archie at first |
15 more |
|
|
| Before |
48 |
33 |
66 |
| Change |
- 5 u |
- 4 u |
- 8 u |
| After |
2 p |
1 p |
2 p |
Number of pens that Archie had at first
= (81 - 15) ÷ 2
= 66 ÷ 2
= 33
Number of pens that Zeph had at first
= 33 + 15
= 48
Number of pens that Archie sold in percent
= 100% - 20%
= 80%
80% =
80100 =
45 Make p the same.
(1) = (3)
48 - 5 u = 66 - 8 u
8 u - 5 u = 66 - 48
3 u = 18
1 u = 18 ÷ 3 = 6
Number of pens that Zeph had left
= 48 - 5 u
= 48 - 5 x 6
= 48 - 30
= 18
Answer(s): 18
