At the end of August, Zoe had four times as many 10-cent coins as 50-cent coins in her piggy bank. She took out 80 10-cent coins and exchanged it for 50-cent coins of the same value. In September, she saved another 18 10-cent coins and some 50-cent coins. She then had four times as many 50-cent coins in the end. She had 350 coins in the end. How many 50-cent coins did she save in September?
|
10-cent |
50-cent |
Total |
Before |
4 u |
1 u |
|
Change 1 |
- 80 |
+ 16 |
|
Change 2 |
+ 18 |
+ ? |
|
After |
1 p |
4 p |
350 |
Total number of coins in the end
= 1 p + 4 p
= 5 p
5 p = 350
1 p = 350 ÷ 5 = 70
Number of 10-cent in the end
= 1 p
= 70
Number of 10-cent at first
= 70 - 18 + 80
= 132
4 u = 132
1 u = 132 ÷ 4 = 33
Number of 50-cent coins in the end
= 4 p
= 4 x 70
= 280
Total value of 80 10-cent coins
= 80 x 10
= 800¢
Number of 50-cent coins that was exchanged from 80 10-cent coins
= 800 ÷ 50
= 16
Number of 50-cent coins that Zoe saved in September
= 4 p - 1 u - 16
= 280 - 33 - 16
= 231
Answer(s): 231