9 days ago, Cindy had a total of 225 grey and red erasers. 20% of her erasers were red erasers. Today, her father gave her some more erasers. As a result, her grey erasers increased by 40%. Now, 50% of her erasers are red erasers. How many red erasers did her father give her?
| |
Red erasers |
Grey erasers |
Total
erasers |
| Before |
1 u |
4 u |
225 |
| Change |
+ 4.6 u |
+ 1.6 u |
|
| After |
5.6 u |
5.6 u |
|
Comparing the
grey erasers and
red erasers in the end |
1 |
1 |
|
20% =
20100 =
15 Red erasers : Grey erasers = 1 : 4
Increase in the number of grey erasers
= 40% x 4 u
=
40100 x 4 u
= 1.6 u
50% =
50100 =
12 In the end
Red erasers : Grey erasers = 1 : 1
Number of erasers at first
= 4 u + 1 u
= 5 u
5 u = 225
1 u = 225 ÷ 5 = 45
Number of red erasers that Cindy received from her father
= 5.6 u - 1 u
= 4.6 u
= 4.6 x 45
= 207
Answer(s): 207
