At the end of August, Hilda had thrice as many 10-cent coins as 50-cent coins in her piggy bank. She took out 95 10-cent coins and exchanged it for 50-cent coins of the same value. In September, she saved another 49 10-cent coins and some 50-cent coins. She then had twice as many 50-cent coins in the end. She had 240 coins in the end. How many 50-cent coins did she save in September?
| |
10-cent |
50-cent |
Total |
| Before |
3 u |
1 u |
|
| Change 1 |
- 95 |
+ 19 |
|
| Change 2 |
+ 49 |
+ ? |
|
| After |
1 p |
2 p |
240 |
Total number of coins in the end
= 1 p + 2 p
= 3 p
3 p = 240
1 p = 240 ÷ 3 = 80
Number of 10-cent in the end
= 1 p
= 80
Number of 10-cent at first
= 80 - 49 + 95
= 126
3 u = 126
1 u = 126 ÷ 3 = 42
Number of 50-cent coins in the end
= 2 p
= 2 x 80
= 160
Total value of 95 10-cent coins
= 95 x 10
= 950¢
Number of 50-cent coins that was exchanged from 95 10-cent coins
= 950 ÷ 50
= 19
Number of 50-cent coins that Hilda saved in September
= 2 p - 1 u - 19
= 160 - 42 - 19
= 99
Answer(s): 99
