At the end of April, Shannon had twice as many 20-cent coins as 50-cent coins in her piggy bank. She took out 50 20-cent coins and exchanged it for 50-cent coins of the same value. In May, she saved another 52 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 May?
|
20-cent |
50-cent |
Total |
Before |
2 u |
1 u |
|
Change 1 |
- 50 |
+ 20 |
|
Change 2 |
+ 52 |
+ ? |
|
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 - 52 + 50
= 78
2 u = 78
1 u = 78 ÷ 2 = 39
Number of 50-cent coins in the end
= 2 p
= 2 x 80
= 160
Total value of 50 20-cent coins
= 50 x 20
= 1000¢
Number of 50-cent coins that was exchanged from 50 20-cent coins
= 1000 ÷ 50
= 20
Number of 50-cent coins that Shannon saved in May
= 2 p - 1 u - 20
= 160 - 39 - 20
= 101
Answer(s): 101