At the end of September, Abi had four times as many 20-cent coins as 50-cent coins in her piggy bank. She took out 70 20-cent coins and exchanged it for 50-cent coins of the same value. In October, she saved another 30 20-cent coins and some 50-cent coins. She then had four times as many 50-cent coins in the end. She had 400 coins in the end. How many 50-cent coins did she save in October?
|
20-cent |
50-cent |
Total |
Before |
4 u |
1 u |
|
Change 1 |
- 70 |
+ 28 |
|
Change 2 |
+ 30 |
+ ? |
|
After |
1 p |
4 p |
400 |
Total number of coins in the end
= 1 p + 4 p
= 5 p
5 p = 400
1 p = 400 ÷ 5 = 80
Number of 20-cent in the end
= 1 p
= 80
Number of 20-cent at first
= 80 - 30 + 70
= 120
4 u = 120
1 u = 120 ÷ 4 = 30
Number of 50-cent coins in the end
= 4 p
= 4 x 80
= 320
Total value of 70 20-cent coins
= 70 x 20
= 1400¢
Number of 50-cent coins that was exchanged from 70 20-cent coins
= 1400 ÷ 50
= 28
Number of 50-cent coins that Abi saved in October
= 4 p - 1 u - 28
= 320 - 30 - 28
= 262
Answer(s): 262