At the end of October, Eva had twice as many 20-cent coins as 50-cent coins in her piggy bank. She took out 95 20-cent coins and exchanged it for 50-cent coins of the same value. In November, she saved another 35 20-cent coins and some 50-cent coins. She then had four times as many 50-cent coins in the end. She had 200 coins in the end. How many 50-cent coins did she save in November?
|
20-cent |
50-cent |
Total |
Before |
2 u |
1 u |
|
Change 1 |
- 95 |
+ 38 |
|
Change 2 |
+ 35 |
+ ? |
|
After |
1 p |
4 p |
200 |
Total number of coins in the end
= 1 p + 4 p
= 5 p
5 p = 200
1 p = 200 ÷ 5 = 40
Number of 20-cent in the end
= 1 p
= 40
Number of 20-cent at first
= 40 - 35 + 95
= 100
2 u = 100
1 u = 100 ÷ 2 = 50
Number of 50-cent coins in the end
= 4 p
= 4 x 40
= 160
Total value of 95 20-cent coins
= 95 x 20
= 1900¢
Number of 50-cent coins that was exchanged from 95 20-cent coins
= 1900 ÷ 50
= 38
Number of 50-cent coins that Eva saved in November
= 4 p - 1 u - 38
= 160 - 50 - 38
= 72
Answer(s): 72