David and Tim had 89 files together. David had 23 more files than Tim. Both of them sold some of their files. Tim sold 40% less files than what David sold. In the end, Tim had half as many files left as David. How many files had David left?
| |
David
(1) |
Tim
(2) |
Make p the same
(2)x2 = (3) |
Comparing David
and Tim at first |
23 more |
|
|
| Before |
56 |
33 |
66 |
| Change |
- 5 u |
- 3 u |
- 6 u |
| After |
2 p |
1 p |
2 p |
Number of files that Tim had at first
= (89 - 23) ÷ 2
= 66 ÷ 2
= 33
Number of files that David had at first
= 33 + 23
= 56
Number of files that Tim sold in percent
= 100% - 40%
= 60%
60% =
60100 =
35 Make p the same.
(1) = (3)
56 - 5 u = 66 - 6 u
6 u - 5 u = 66 - 56
1 u = 10
1 u = 10 ÷ 1 = 10
Number of files that David had left
= 56 - 5 u
= 56 - 5 x 10
= 56 - 50
= 6
Answer(s): 6
