9 days ago, Julie had a total of 100 yellow and purple marbles. 30% of her marbles were purple marbles. Today, her grandfather gave her some more marbles. As a result, her yellow marbles increased by 20%. Now, 50% of her marbles are purple marbles. How many purple marbles did her grandfather give her?
| |
Purple marbles |
Yellow marbles |
Total
marbles |
| Before |
3 u |
7 u |
100 |
| Change |
+ 5.4 u |
+ 1.4 u |
|
| After |
8.4 u |
8.4 u |
|
Comparing the
yellow marbles and
purple marbles in the end |
1 |
1 |
|
30% =
30100 =
310 Purple marbles : Yellow marbles = 3 : 7
Increase in the number of yellow marbles
= 20% x 7 u
=
20100 x 7 u
= 1.4 u
50% =
50100 =
12 In the end
Purple marbles : Yellow marbles = 1 : 1
Number of marbles at first
= 7 u + 3 u
= 10 u
10 u = 100
1 u = 100 ÷ 10 = 10
Number of purple marbles that Julie received from her grandfather
= 8.4 u - 3 u
= 5.4 u
= 5.4 x 10
= 54
Answer(s): 54
