The number of ten-cent coins in a bottle was
15 the number of twenty-cent coins. Vincent took out 23 twenty-cent coins and exchanged them for ten-cent coins. Then he put the money back into the bottle. The number of twenty-cent coins became
25 the number of ten-cent coins. How much money was there in the bottle?
|
Make u the same (1)x5 = (3) |
10-cent (1) |
20-cent (2) |
Before |
5 u |
1 u |
5 u |
Change |
+ 230 |
+ 46 |
- 23 |
After |
25 p |
5 p |
2 p |
Value of 20-cent coins to be exchanged to 10-cent coins
= 23 x 20
= 460
Number of 10-cent coins to be exchanged from the 20-cent coins
= 460 ÷ 10
= 46
(3) = (2)
25 p - 230 = 2 p + 23
25 p - 2 p = 23 + 230
23 p = 253
1 p = 253 ÷ 23 = 11
Number of 10-cent coins in the end
= 5 p
= 5 p x 11
= 55
Value of 10-cent coins in the end
= 55 x 10
= 550¢
Number of 20-cent coins in the end
= 2 p
= 2 x 11
= 22
Value of 20-cent coins in the end
= 22 x 20
= 440¢
Total value of coins
= 550 + 440
= 990¢
$1 = 100¢
990¢ = $9.90
Answer(s): $9.90