PSLE Justin had red pencils and silver pencils for sale. He sold 210 red pencils. 70% of the pencils sold were silver.
- How many red pencils and silver pencils did Justin sell altogether?
- He sold 50% of his pencils. 70% of the pencils left unsold were red. How many silver pencils did Justin have at first?
| |
Red |
Silver |
Total |
Total in percent |
| Before |
10 u |
10 u |
20 u |
100% |
| Change |
- 30%
- 3 u |
- 70%
- 7 u |
- 100%
- 10 u |
- 50% |
| After |
70%
7 u |
30%
3 u |
100%
10 u |
50%
|
70% =
70100 =
710 Total number of pencils sold = 10 u
Number of silver pencils sold = 7 u
Number of red pencils sold
= 10 u - 7 u
= 3 u
3 u = 210
1 u = 210 ÷ 3 = 70
Total number of pencils sold
= 10 u
= 10 x 70
= 700
(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 red = 70%
Percent of the pencils left unsold that were silver = 100% - 70% = 30%
Number of the pencils left unsold that were silver
= 30% x 10 u
=
30100 x 10 u
= 3 u
Number of silver pencils that Justin had at first
= 3 u + 7 u
= 10 u
= 10 x 70
= 700
Answer(s): (a) 700; (b) 700
