Oscar and Luis had 207 pens together. Oscar had 21 more pens than Luis. Both of them sold some of their pens. Luis sold 10% less pens than what Oscar sold. In the end, Luis had half as many pens left as Oscar. How many pens had Oscar left?
| |
Oscar
(1) |
Luis
(2) |
Make p the same
(2)x2 = (3) |
Comparing Oscar
and Luis at first |
21 more |
|
|
| Before |
114 |
93 |
186 |
| Change |
- 10 u |
- 9 u |
- 18 u |
| After |
2 p |
1 p |
2 p |
Number of pens that Luis had at first
= (207 - 21) ÷ 2
= 186 ÷ 2
= 93
Number of pens that Oscar had at first
= 93 + 21
= 114
Number of pens that Luis sold in percent
= 100% - 10%
= 90%
90% =
90100 =
910 Make p the same.
(1) = (3)
114 - 10 u = 186 - 18 u
18 u - 10 u = 186 - 114
8 u = 72
1 u = 72 ÷ 8 = 9
Number of pens that Oscar had left
= 114 - 10 u
= 114 - 10 x 9
= 114 - 90
= 24
Answer(s): 24
