3 days ago, Irene had a total of 250 gold and grey cards. 40% of her cards were grey cards. Today, her older brother gave her some more cards. As a result, her gold cards increased by 20%. Now, 50% of her cards are grey cards. How many grey cards did her older brother give her?
| |
Grey cards |
Gold cards |
Total
cards |
| Before |
2 u |
3 u |
250 |
| Change |
+ 1.6 u |
+ 0.6 u |
|
| After |
3.6 u |
3.6 u |
|
Comparing the
gold cards and
grey cards in the end |
1 |
1 |
|
40% =
40100 =
25 Grey cards : Gold cards = 2 : 3
Increase in the number of gold cards
= 20% x 3 u
=
20100 x 3 u
= 0.6 u
50% =
50100 =
12 In the end
Grey cards : Gold cards = 1 : 1
Number of cards at first
= 3 u + 2 u
= 5 u
5 u = 250
1 u = 250 ÷ 5 = 50
Number of grey cards that Irene received from her older brother
= 3.6 u - 2 u
= 1.6 u
= 1.6 x 50
= 80
Answer(s): 80
