PSLE Andy had a total of 40 coins in his coin box.
310 of all the coins saved were one-dollar coins. There were 2 times as many one-dollar coins as ten-cent coins. The remaining coins were twenty-cent coins. What was the total value of all the coins in his coin box?
|
One-dollar |
Ten-cent |
Twenty-cent |
Total |
Comparison between the number of 3 types of coins |
3x2 6 u |
7x2 14 u |
10x2 20 u
|
Comparison between the number of one-dollar and ten-cent coins |
2x3 |
1x3 |
|
|
Number |
6 u |
3 u |
11 u |
20 u |
Value |
1 |
0.1 |
0.2 |
|
Number x value |
6 u |
0.3 u |
2.2 u |
8.5 u |
Number of $1 coins is the repeated identity.
Make the number of $1 coins the same.
LCM of 3 and 2 = 6
Total number of coins = 20 u
20 u = 40
1 u = 40 ÷ 20 = 2
Total value of coins
= 6 u 0.3 u 2.2 u
= 8.5 u
= 8.5 x 2
= $17
Answer(s): $17