12 days ago, Mary had a total of 160 gold and white erasers. 25% of her erasers were white erasers. Today, her cousin gave her some more erasers. As a result, her gold erasers increased by 30%. Now, 50% of her erasers are white erasers. How many white erasers did her cousin give her?
| |
White erasers |
Gold erasers |
Total
erasers |
| Before |
1 u |
3 u |
160 |
| Change |
+ 2.9 u |
+ 0.9 u |
|
| After |
3.9 u |
3.9 u |
|
Comparing the
gold erasers and
white erasers in the end |
1 |
1 |
|
25% =
25100 =
14 White erasers : Gold erasers = 1 : 3
Increase in the number of gold erasers
= 30% x 3 u
=
30100 x 3 u
= 0.9 u
50% =
50100 =
12 In the end
White erasers : Gold erasers = 1 : 1
Number of erasers at first
= 3 u + 1 u
= 4 u
4 u = 160
1 u = 160 ÷ 4 = 40
Number of white erasers that Mary received from her cousin
= 3.9 u - 1 u
= 2.9 u
= 2.9 x 40
= 116
Answer(s): 116
