PSLE Ben saved a total of $21 in coins in his coin box.
12 of all the coins saved were one-dollar coins. There were 3 times as many one-dollar coins as ten-cent coins. The remaining coins were twenty-cent coins. How many coins did Ben save in his coin box altogether?
|
One-dollar |
Ten-cent |
Twenty-cent |
Total |
Comparison between the number of 3 types of coins |
1x3 3 u |
1x3 3 u |
2x3 6 u
|
Comparison between the number of one-dollar and ten-cent coins |
3x1 |
1x1 |
|
|
Number |
3 u |
1 u |
2 u |
6 u |
Value |
1 |
0.1 |
0.2 |
|
Number x value |
3 u |
0.1 u |
0.4 u |
3.5 u |
Number of $1 coins is the repeated identity.
Make the number of $1 coins the same.
LCM of 1 and 3 = 3
Total value of coins = 3.5 u
3.5 u = 21
1 u = 21 ÷ 3.5 = 6
Total number of coins
= 3 u + 1 u + 2 u
= 6 u
= 6 x 6
= 36
Answer(s): 36