6 days ago, Yoko had a total of 125 yellow and red coins. 20% of her coins were red coins. Today, her older sister gave her some more coins. As a result, her yellow coins increased by 10%. Now, 50% of her coins are red coins. How many red coins did her older sister give her?
| |
Red coins |
Yellow coins |
Total
coins |
| Before |
1 u |
4 u |
125 |
| Change |
+ 3.4 u |
+ 0.4 u |
|
| After |
4.4 u |
4.4 u |
|
Comparing the
yellow coins and
red coins in the end |
1 |
1 |
|
20% =
20100 =
15 Red coins : Yellow coins = 1 : 4
Increase in the number of yellow coins
= 10% x 4 u
=
10100 x 4 u
= 0.4 u
50% =
50100 =
12 In the end
Red coins : Yellow coins = 1 : 1
Number of coins at first
= 4 u + 1 u
= 5 u
5 u = 125
1 u = 125 ÷ 5 = 25
Number of red coins that Yoko received from her older sister
= 4.4 u - 1 u
= 3.4 u
= 3.4 x 25
= 85
Answer(s): 85
