15 days ago, Wendy had a total of 280 black and yellow erasers. 30% of her erasers were yellow erasers. Today, her grandfather gave her some more erasers. As a result, her black erasers increased by 25%. Now, 50% of her erasers are yellow erasers. How many yellow erasers did her grandfather give her?
| |
Yellow erasers |
Black erasers |
Total
erasers |
| Before |
3 u |
7 u |
280 |
| Change |
+ 5.75 u |
+ 1.75 u |
|
| After |
8.75 u |
8.75 u |
|
Comparing the
black erasers and
yellow erasers in the end |
1 |
1 |
|
30% =
30100 =
310 Yellow erasers : Black erasers = 3 : 7
Increase in the number of black erasers
= 25% x 7 u
=
25100 x 7 u
= 1.75 u
50% =
50100 =
12 In the end
Yellow erasers : Black erasers = 1 : 1
Number of erasers at first
= 7 u + 3 u
= 10 u
10 u = 280
1 u = 280 ÷ 10 = 28
Number of yellow erasers that Wendy received from her grandfather
= 8.75 u - 3 u
= 5.75 u
= 5.75 x 28
= 161
Answer(s): 161
