3 days ago, Kathy had a total of 225 grey and red pens. 40% of her pens were red pens. Today, her uncle gave her some more pens. As a result, her grey pens increased by 20%. Now, 50% of her pens are red pens. How many red pens did her uncle give her?
| |
Red pens |
Grey pens |
Total
pens |
| Before |
2 u |
3 u |
225 |
| Change |
+ 1.6 u |
+ 0.6 u |
|
| After |
3.6 u |
3.6 u |
|
Comparing the
grey pens and
red pens in the end |
1 |
1 |
|
40% =
40100 =
25 Red pens : Grey pens = 2 : 3
Increase in the number of grey pens
= 20% x 3 u
=
20100 x 3 u
= 0.6 u
50% =
50100 =
12 In the end
Red pens : Grey pens = 1 : 1
Number of pens at first
= 3 u + 2 u
= 5 u
5 u = 225
1 u = 225 ÷ 5 = 45
Number of red pens that Kathy received from her uncle
= 3.6 u - 2 u
= 1.6 u
= 1.6 x 45
= 72
Answer(s): 72
