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