PSLE Mark had yellow pencils and blue pencils for sale. He sold 840 yellow pencils. 30% of the pencils sold were blue.
- How many yellow pencils and blue pencils did Mark sell altogether?
- He sold 50% of his pencils. 75% of the pencils left unsold were yellow. How many blue pencils did Mark have at first?
|
Yellow |
Blue |
Total |
Total in percent |
Before |
14.5 u |
5.5 u |
20 u |
100% |
Change |
- 70% - 7 u |
- 30% - 3 u |
- 100% - 10 u |
- 50% |
After |
75% 7.5 u |
25% 2.5 u |
100% 10 u |
50%
|
30% =
30100 =
310 Total number of pencils sold = 10 u
Number of blue pencils sold = 3 u
Number of yellow 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 yellow = 75%
Percent of the pencils left unsold that were blue = 100% - 75% = 25%
Number of the pencils left unsold that were blue
= 25% x 10 u
=
25100 x 10 u
= 2.5 u
Number of blue pencils that Mark had at first
= 2.5 u + 3 u
= 5.5 u
= 5.5 x 120
= 660
Answer(s): (a) 1200; (b) 660