How can we use the concept:
When multiplying decimals, first remove the decimals and multiply like normal, then count how many decimal places there are in both factors, and move the decimal point back into the product that many times.
Sample Math Problems
Question
5.6 x 2
Solution
First remove the decimal and multiply. 56 x 2 = 112
Next, count the number of digits behind the decimal point in the original factors. 5.6 has just one digit behind the decimal point.
Last, since there is one digit behind the decimal point, move the decimal into the answer one place from the right.
The answer is 11.2
Question
2.5 x 0.8
Solution
First remove the decimal and multiply. 25 x 8 = 200
Next, count the number of digits behind the decimal point in both of the original factors. 2.5 has one digit behind the decimal point and 0.8 has one digit behind the decimal point. In total, there are two digits behind the decimal point.
Last, since there are two digits behind the decimal point, move the decimal into the answer two places from the right.
The answer is 2.00 or 2
Question
8.15 x 4.7
Solution
First remove the decimal and multiply. 815 x 47 = 38305
Next, count the number of digits behind the decimal point in both of the original factors. 8.15 has two digits behind the decimal point and 4.7 has one digit behind the decimal point. In total, there are three digits behind the decimal point.
Last, since there are three digits behind the decimal point, move the decimal into the answer three places from the right.
The answer is 38.305
Question
5.49 x 2.83
Solution
First remove the decimal and multiply. 549 x 283 = 155367
Next, count the number of digits behind the decimal point in both of the original factors. 8.49 has two digits behind the decimal point and 2.83 has two digits behind the decimal point. In total, there are four digits behind the decimal point.
Last, since there are four digits behind the decimal point, move the decimal into the answer four places from the right.
The answer is 15.5367
