At the end of January, Vanessa had twice as many 20-cent coins as 50-cent coins in her piggy bank. She took out 70 20-cent coins and exchanged it for 50-cent coins of the same value. In February, she saved another 80 20-cent coins and some 50-cent coins. She then had four times as many 50-cent coins in the end. She had 450 coins in the end. How many 50-cent coins did she save in February?
| |
20-cent |
50-cent |
Total |
| Before |
2 u |
1 u |
|
| Change 1 |
- 70 |
+ 28 |
|
| Change 2 |
+ 80 |
+ ? |
|
| After |
1 p |
4 p |
450 |
Total number of coins in the end
= 1 p + 4 p
= 5 p
5 p = 450
1 p = 450 ÷ 5 = 90
Number of 20-cent in the end
= 1 p
= 90
Number of 20-cent at first
= 90 - 80 + 70
= 80
2 u = 80
1 u = 80 ÷ 2 = 40
Number of 50-cent coins in the end
= 4 p
= 4 x 90
= 360
Total value of 70 20-cent coins
= 70 x 20
= 1400¢
Number of 50-cent coins that was exchanged from 70 20-cent coins
= 1400 ÷ 50
= 28
Number of 50-cent coins that Vanessa saved in February
= 4 p - 1 u - 28
= 360 - 40 - 28
= 292
Answer(s): 292
