6 days ago, Lucy had a total of 100 green and purple stamps. 20% of her stamps were purple stamps. Today, her mother gave her some more stamps. As a result, her green stamps increased by 30%. Now, 50% of her stamps are purple stamps. How many purple stamps did her mother give her?
| |
Purple stamps |
Green stamps |
Total
stamps |
| Before |
1 u |
4 u |
100 |
| Change |
+ 4.2 u |
+ 1.2 u |
|
| After |
5.2 u |
5.2 u |
|
Comparing the
green stamps and
purple stamps in the end |
1 |
1 |
|
20% =
20100 =
15 Purple stamps : Green stamps = 1 : 4
Increase in the number of green stamps
= 30% x 4 u
=
30100 x 4 u
= 1.2 u
50% =
50100 =
12 In the end
Purple stamps : Green stamps = 1 : 1
Number of stamps at first
= 4 u + 1 u
= 5 u
5 u = 100
1 u = 100 ÷ 5 = 20
Number of purple stamps that Lucy received from her mother
= 5.2 u - 1 u
= 4.2 u
= 4.2 x 20
= 84
Answer(s): 84
