At the end of May, Penelope had four times as many 20-cent coins as 50-cent coins in her piggy bank. She took out 100 20-cent coins and exchanged it for 50-cent coins of the same value. In June, she saved another 46 20-cent coins and some 50-cent coins. She then had four times as many 50-cent coins in the end. She had 450 coins in the end. How many 50-cent coins did she save in June?
|
20-cent |
50-cent |
Total |
Before |
4 u |
1 u |
|
Change 1 |
- 100 |
+ 40 |
|
Change 2 |
+ 46 |
+ ? |
|
After |
1 p |
4 p |
450 |
Total number of coins in the end
= 1 p + 4 p
= 5 p
5 p = 450
1 p = 450 ÷ 5 = 90
Number of 20-cent in the end
= 1 p
= 90
Number of 20-cent at first
= 90 - 46 + 100
= 144
4 u = 144
1 u = 144 ÷ 4 = 36
Number of 50-cent coins in the end
= 4 p
= 4 x 90
= 360
Total value of 100 20-cent coins
= 100 x 20
= 2000¢
Number of 50-cent coins that was exchanged from 100 20-cent coins
= 2000 ÷ 50
= 40
Number of 50-cent coins that Penelope saved in June
= 4 p - 1 u - 40
= 360 - 36 - 40
= 284
Answer(s): 284