PSLE Ian had blue pencils and red pencils for sale. He sold 840 blue pencils. 30% of the pencils sold were red.
- How many blue pencils and red pencils did Ian sell altogether?
- He sold 50% of his pencils. 60% of the pencils left unsold were blue. How many red pencils did Ian have at first?
| |
Blue |
Red |
Total |
Total in percent |
| Before |
13 u |
7 u |
20 u |
100% |
| Change |
- 70%
- 7 u |
- 30%
- 3 u |
- 100%
- 10 u |
- 50% |
| After |
60%
6 u |
40%
4 u |
100%
10 u |
50%
|
30% =
30100 =
310 Total number of pencils sold = 10 u
Number of red pencils sold = 3 u
Number of blue pencils sold
= 10 u - 3 u
= 7 u
7 u = 840
1 u = 840 ÷ 7 = 120
Total number of pencils sold
= 10 u
= 10 x 120
= 1200
(b)
Percent of the pencils left unsold = 100% - 50% = 50% 50% of the pencils that were sold = 10 u 50% of the pencils that were left unsold = 10 u Percent of the pencils left unsold that were blue = 60%
Percent of the pencils left unsold that were red = 100% - 60% = 40%
Number of the pencils left unsold that were red
= 40% x 10 u
=
40100 x 10 u
= 4 u
Number of red pencils that Ian had at first
= 4 u + 3 u
= 7 u
= 7 x 120
= 840
Answer(s): (a) 1200; (b) 840
