At the end of February, Elyse 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 March, she saved another 7 20-cent coins and some 50-cent coins. She then had thrice as many 50-cent coins in the end. She had 200 coins in the end. How many 50-cent coins did she save in March?
|
20-cent |
50-cent |
Total |
Before |
4 u |
1 u |
|
Change 1 |
- 85 |
+ 34 |
|
Change 2 |
+ 7 |
+ ? |
|
After |
1 p |
3 p |
200 |
Total number of coins in the end
= 1 p + 3 p
= 4 p
4 p = 200
1 p = 200 ÷ 4 = 50
Number of 20-cent in the end
= 1 p
= 50
Number of 20-cent at first
= 50 - 7 + 85
= 128
4 u = 128
1 u = 128 ÷ 4 = 32
Number of 50-cent coins in the end
= 3 p
= 3 x 50
= 150
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 Elyse saved in March
= 3 p - 1 u - 34
= 150 - 32 - 34
= 84
Answer(s): 84