At the end of October, Kathy had twice as many 20-cent coins as 50-cent coins in her piggy bank. She took out 65 20-cent coins and exchanged it for 50-cent coins of the same value. In November, she saved another 85 20-cent coins and some 50-cent coins. She then had thrice as many 50-cent coins in the end. She had 360 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 |
- 65 |
+ 26 |
|
Change 2 |
+ 85 |
+ ? |
|
After |
1 p |
3 p |
360 |
Total number of coins in the end
= 1 p + 3 p
= 4 p
4 p = 360
1 p = 360 ÷ 4 = 90
Number of 20-cent in the end
= 1 p
= 90
Number of 20-cent at first
= 90 - 85 + 65
= 70
2 u = 70
1 u = 70 ÷ 2 = 35
Number of 50-cent coins in the end
= 3 p
= 3 x 90
= 270
Total value of 65 20-cent coins
= 65 x 20
= 1300¢
Number of 50-cent coins that was exchanged from 65 20-cent coins
= 1300 ÷ 50
= 26
Number of 50-cent coins that Kathy saved in November
= 3 p - 1 u - 26
= 270 - 35 - 26
= 209
Answer(s): 209