9 days ago, Mary had a total of 200 purple and white stamps. 20% of her stamps were white stamps. Today, her older sister gave her some more stamps. As a result, her purple stamps increased by 40%. Now, 50% of her stamps are white stamps. How many white stamps did her older sister give her?
| |
White stamps |
Purple stamps |
Total
stamps |
| Before |
1 u |
4 u |
200 |
| Change |
+ 4.6 u |
+ 1.6 u |
|
| After |
5.6 u |
5.6 u |
|
Comparing the
purple stamps and
white stamps in the end |
1 |
1 |
|
20% =
20100 =
15 White stamps : Purple stamps = 1 : 4
Increase in the number of purple stamps
= 40% x 4 u
=
40100 x 4 u
= 1.6 u
50% =
50100 =
12 In the end
White stamps : Purple stamps = 1 : 1
Number of stamps at first
= 4 u + 1 u
= 5 u
5 u = 200
1 u = 200 ÷ 5 = 40
Number of white stamps that Mary received from her older sister
= 5.6 u - 1 u
= 4.6 u
= 4.6 x 40
= 184
Answer(s): 184
