6 days ago, Abi had a total of 200 brown and black pens. 20% of her pens were black pens. Today, her older brother gave her some more pens. As a result, her brown pens increased by 30%. Now, 50% of her pens are black pens. How many black pens did her older brother give her?
| |
Black pens |
Brown pens |
Total
pens |
| Before |
1 u |
4 u |
200 |
| Change |
+ 4.2 u |
+ 1.2 u |
|
| After |
5.2 u |
5.2 u |
|
Comparing the
brown pens and
black pens in the end |
1 |
1 |
|
20% =
20100 =
15 Black pens : Brown pens = 1 : 4
Increase in the number of brown pens
= 30% x 4 u
=
30100 x 4 u
= 1.2 u
50% =
50100 =
12 In the end
Black pens : Brown pens = 1 : 1
Number of pens at first
= 4 u + 1 u
= 5 u
5 u = 200
1 u = 200 ÷ 5 = 40
Number of black pens that Abi received from her older brother
= 5.2 u - 1 u
= 4.2 u
= 4.2 x 40
= 168
Answer(s): 168
