7 days ago, Lucy had a total of 200 blue and silver pens. 30% of her pens were silver pens. Today, her grandfather gave her some more pens. As a result, her blue pens increased by 20%. Now, 50% of her pens are silver pens. How many silver pens did her grandfather give her?
| |
Silver pens |
Blue pens |
Total
pens |
| Before |
3 u |
7 u |
200 |
| Change |
+ 5.4 u |
+ 1.4 u |
|
| After |
8.4 u |
8.4 u |
|
Comparing the
blue pens and
silver pens in the end |
1 |
1 |
|
30% =
30100 =
310 Silver pens : Blue pens = 3 : 7
Increase in the number of blue pens
= 20% x 7 u
=
20100 x 7 u
= 1.4 u
50% =
50100 =
12 In the end
Silver pens : Blue pens = 1 : 1
Number of pens at first
= 7 u + 3 u
= 10 u
10 u = 200
1 u = 200 ÷ 10 = 20
Number of silver pens that Lucy received from her grandfather
= 8.4 u - 3 u
= 5.4 u
= 5.4 x 20
= 108
Answer(s): 108
