7 days ago, Emily had a total of 250 yellow and red stamps. 30% of her stamps were red stamps. Today, her father gave her some more stamps. As a result, her yellow stamps increased by 20%. Now, 50% of her stamps are red stamps. How many red stamps did her father give her?
| |
Red stamps |
Yellow stamps |
Total
stamps |
| Before |
3 u |
7 u |
250 |
| Change |
+ 5.4 u |
+ 1.4 u |
|
| After |
8.4 u |
8.4 u |
|
Comparing the
yellow stamps and
red stamps in the end |
1 |
1 |
|
30% =
30100 =
310 Red stamps : Yellow stamps = 3 : 7
Increase in the number of yellow stamps
= 20% x 7 u
=
20100 x 7 u
= 1.4 u
50% =
50100 =
12 In the end
Red stamps : Yellow stamps = 1 : 1
Number of stamps at first
= 7 u + 3 u
= 10 u
10 u = 250
1 u = 250 ÷ 10 = 25
Number of red stamps that Emily received from her father
= 8.4 u - 3 u
= 5.4 u
= 5.4 x 25
= 135
Answer(s): 135
