Riordan and Zeph had 90 notebooks together. Riordan had 16 more notebooks than Zeph. Both of them sold some of their notebooks. Zeph sold 20% less notebooks than what Riordan sold. In the end, Zeph had half as many notebooks left as Riordan. How many notebooks had Riordan left?
| |
Riordan
(1) |
Zeph
(2) |
Make p the same
(2)x2 = (3) |
Comparing Riordan
and Zeph at first |
16 more |
|
|
| Before |
53 |
37 |
74 |
| Change |
- 5 u |
- 4 u |
- 8 u |
| After |
2 p |
1 p |
2 p |
Number of notebooks that Zeph had at first
= (90 - 16) ÷ 2
= 74 ÷ 2
= 37
Number of notebooks that Riordan had at first
= 37 + 16
= 53
Number of notebooks that Zeph sold in percent
= 100% - 20%
= 80%
80% =
80100 =
45 Make p the same.
(1) = (3)
53 - 5 u = 74 - 8 u
8 u - 5 u = 74 - 53
3 u = 21
1 u = 21 ÷ 3 = 7
Number of notebooks that Riordan had left
= 53 - 5 u
= 53 - 5 x 7
= 53 - 35
= 18
Answer(s): 18
