The number of ten-cent coins in a bottle was
14 the number of twenty-cent coins. Henry took out 21 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
58 the number of ten-cent coins. How much money was there in the bottle?
|
Make u the same (1)x4 = (3) |
10-cent (1) |
20-cent (2) |
Before |
4 u |
1 u |
4 u |
Change |
+ 168 |
+ 42 |
- 21 |
After |
32 p |
8 p |
5 p |
Value of 20-cent coins to be exchanged to 10-cent coins
= 21 x 20
= 420
Number of 10-cent coins to be exchanged from the 20-cent coins
= 420 ÷ 10
= 42
(3) = (2)
32 p - 168 = 5 p + 21
32 p - 5 p = 21 + 168
27 p = 189
1 p = 189 ÷ 27 = 7
Number of 10-cent coins in the end
= 8 p
= 8 p x 7
= 56
Value of 10-cent coins in the end
= 56 x 10
= 560¢
Number of 20-cent coins in the end
= 5 p
= 5 x 7
= 35
Value of 20-cent coins in the end
= 35 x 20
= 700¢
Total value of coins
= 560 + 700
= 1260¢
$1 = 100¢
1260¢ = $12.60
Answer(s): $12.60