3 days ago, Shannon had a total of 275 black and blue stamps. 20% of her stamps were blue stamps. Today, her grandmother gave her some more stamps. As a result, her black stamps increased by 30%. Now, 50% of her stamps are blue stamps. How many blue stamps did her grandmother give her?
| |
Blue stamps |
Black stamps |
Total
stamps |
| Before |
1 u |
4 u |
275 |
| Change |
+ 4.2 u |
+ 1.2 u |
|
| After |
5.2 u |
5.2 u |
|
Comparing the
black stamps and
blue stamps in the end |
1 |
1 |
|
20% =
20100 =
15 Blue stamps : Black stamps = 1 : 4
Increase in the number of black stamps
= 30% x 4 u
=
30100 x 4 u
= 1.2 u
50% =
50100 =
12 In the end
Blue stamps : Black stamps = 1 : 1
Number of stamps at first
= 4 u + 1 u
= 5 u
5 u = 275
1 u = 275 ÷ 5 = 55
Number of blue stamps that Shannon received from her grandmother
= 5.2 u - 1 u
= 4.2 u
= 4.2 x 55
= 231
Answer(s): 231
