At the end of October, Jean 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 November, she saved another 4 10-cent coins and some 50-cent coins. She then had thrice as many 50-cent coins in the end. She had 320 coins in the end. How many 50-cent coins did she save in November?
|
10-cent |
50-cent |
Total |
Before |
3 u |
1 u |
|
Change 1 |
- 95 |
+ 19 |
|
Change 2 |
+ 4 |
+ ? |
|
After |
1 p |
3 p |
320 |
Total number of coins in the end
= 1 p + 3 p
= 4 p
4 p = 320
1 p = 320 ÷ 4 = 80
Number of 10-cent in the end
= 1 p
= 80
Number of 10-cent at first
= 80 - 4 + 95
= 171
3 u = 171
1 u = 171 ÷ 3 = 57
Number of 50-cent coins in the end
= 3 p
= 3 x 80
= 240
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 Jean saved in November
= 3 p - 1 u - 19
= 240 - 57 - 19
= 164
Answer(s): 164