PSLE Ben had pink notebooks and red notebooks for sale. He sold 770 pink notebooks. 30% of the notebooks sold were red.
- How many pink notebooks and red notebooks did Ben sell altogether?
- He sold 50% of his notebooks. 80% of the notebooks left unsold were pink. How many red notebooks did Ben have at first?
| |
Pink |
Red |
Total |
Total in percent |
| Before |
15 u |
5 u |
20 u |
100% |
| Change |
- 70%
- 7 u |
- 30%
- 3 u |
- 100%
- 10 u |
- 50% |
| After |
80%
8 u |
20%
2 u |
100%
10 u |
50%
|
30% =
30100 =
310 Total number of notebooks sold = 10 u
Number of red notebooks sold = 3 u
Number of pink notebooks sold
= 10 u - 3 u
= 7 u
7 u = 770
1 u = 770 ÷ 7 = 110
Total number of notebooks sold
= 10 u
= 10 x 110
= 1100
(b)
Percent of the notebooks left unsold = 100% - 50% = 50% 50% of the notebooks that were sold = 10 u 50% of the notebooks that were left unsold = 10 u Percent of the notebooks left unsold that were pink = 80%
Percent of the notebooks left unsold that were red = 100% - 80% = 20%
Number of the notebooks left unsold that were red
= 20% x 10 u
=
20100 x 10 u
= 2 u
Number of red notebooks that Ben had at first
= 2 u + 3 u
= 5 u
= 5 x 110
= 550
Answer(s): (a) 1100; (b) 550
