At the end of July, Joelle had thrice as many 20-cent coins as 50-cent coins in her piggy bank. She took out 60 20-cent coins and exchanged it for 50-cent coins of the same value. In August, she saved another 20 20-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 August?
|
20-cent |
50-cent |
Total |
Before |
3 u |
1 u |
|
Change 1 |
- 60 |
+ 24 |
|
Change 2 |
+ 20 |
+ ? |
|
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 20-cent in the end
= 1 p
= 80
Number of 20-cent at first
= 80 - 20 + 60
= 120
3 u = 120
1 u = 120 ÷ 3 = 40
Number of 50-cent coins in the end
= 2 p
= 2 x 80
= 160
Total value of 60 20-cent coins
= 60 x 20
= 1200¢
Number of 50-cent coins that was exchanged from 60 20-cent coins
= 1200 ÷ 50
= 24
Number of 50-cent coins that Joelle saved in August
= 2 p - 1 u - 24
= 160 - 40 - 24
= 96
Answer(s): 96