PSLE Bobby saved a total of $30 in coins in his coin box.
18 of all the coins saved were one-dollar coins. There were 3 times as many one-dollar coins as fifty-cent coins. The remaining coins were twenty-cent coins. How many coins did Bobby save in his coin box altogether?
|
One-dollar |
Fifty-cent |
Twenty-cent |
Total |
Comparison between the number of 3 types of coins |
1x3 3 u |
7x3 21 u |
8x3 24 u
|
Comparison between the number of one-dollar and fifty-cent coins |
3x1 |
1x1 |
|
|
Number |
3 u |
1 u |
20 u |
24 u |
Value |
1 |
0.5 |
0.2 |
|
Number x value |
3 u |
0.5 u |
4 u |
7.5 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 = 7.5 u
7.5 u = 30
1 u = 30 ÷ 7.5 = 4
Total number of coins
= 3 u + 1 u + 20 u
= 24 u
= 24 x 4
= 96
Answer(s): 96