TLDR;
This video explains how to multiply decimals by decimals in three steps: removing the decimals and multiplying as whole numbers, then placing the decimal in the correct spot in the answer. The number of digits to the right of the decimal in the factors determines the placement in the product.
- Remove decimals and multiply whole numbers.
- Count digits to the right of decimals in the original problem.
- Place the decimal in the answer so it has the same number of digits to the right.
Multiplying 72 Hundredths by 4 Tenths [0:10]
To multiply 72 hundredths by 4 tenths, first remove the decimals and rewrite the problem as 72 times 4. Multiply these whole numbers to get 288. Then, count the total number of digits to the right of the decimals in the original problem (three: 7, 2, and 4). Place the decimal in the answer so that there are three digits to the right, resulting in 288 thousandths.
Multiplying 6 and 3 Tenths by 2 and 9 Tenths [2:11]
To multiply 6 and 3 tenths by 2 and 9 tenths, remove the decimals and multiply 63 by 29. This multiplication yields 1,827. Count the digits to the right of the decimal in the original problem (two: 3 and 9). Place the decimal in the answer so that there are two digits to the right, giving a final answer of 18 and 27 hundredths.
