At the end of July, Shannon had four times as many 20-cent coins as 50-cent coins in her piggy bank. She took out 85 20-cent coins and exchanged it for 50-cent coins of the same value. In August, she saved another 1 20-cent coins and some 50-cent coins. She then had twice as many 50-cent coins in the end. She had 300 coins in the end. How many 50-cent coins did she save in August?
| |
20-cent |
50-cent |
Total |
| Before |
4 u |
1 u |
|
| Change 1 |
- 85 |
+ 34 |
|
| Change 2 |
+ 1 |
+ ? |
|
| After |
1 p |
2 p |
300 |
Total number of coins in the end
= 1 p + 2 p
= 3 p
3 p = 300
1 p = 300 ÷ 3 = 100
Number of 20-cent in the end
= 1 p
= 100
Number of 20-cent at first
= 100 - 1 + 85
= 184
4 u = 184
1 u = 184 ÷ 4 = 46
Number of 50-cent coins in the end
= 2 p
= 2 x 100
= 200
Total value of 85 20-cent coins
= 85 x 20
= 1700¢
Number of 50-cent coins that was exchanged from 85 20-cent coins
= 1700 ÷ 50
= 34
Number of 50-cent coins that Shannon saved in August
= 2 p - 1 u - 34
= 200 - 46 - 34
= 120
Answer(s): 120
