10 days ago, Sarah had a total of 100 green and gold marbles. 25% of her marbles were gold marbles. Today, her younger brother gave her some more marbles. As a result, her green marbles increased by 40%. Now, 50% of her marbles are gold marbles. How many gold marbles did her younger brother give her?
| |
Gold marbles |
Green marbles |
Total
marbles |
| Before |
1 u |
3 u |
100 |
| Change |
+ 3.2 u |
+ 1.2 u |
|
| After |
4.2 u |
4.2 u |
|
Comparing the
green marbles and
gold marbles in the end |
1 |
1 |
|
25% =
25100 =
14 Gold marbles : Green marbles = 1 : 3
Increase in the number of green marbles
= 40% x 3 u
=
40100 x 3 u
= 1.2 u
50% =
50100 =
12 In the end
Gold marbles : Green marbles = 1 : 1
Number of marbles at first
= 3 u + 1 u
= 4 u
4 u = 100
1 u = 100 ÷ 4 = 25
Number of gold marbles that Sarah received from her younger brother
= 4.2 u - 1 u
= 3.2 u
= 3.2 x 25
= 80
Answer(s): 80
