Applying the Rule for Decimal Point Placement
Applying the rule for decimal point placement is a Grade 6 math skill in Big Ideas Math Advanced 1, Chapter 2: Fractions and Decimals. Students learn that when multiplying or dividing decimals, the position of the decimal point is determined by counting decimal places — the total decimal places in both factors determines the placement in the product.
Key Concepts
When multiplying decimals, count the total decimal places in both factors to determine decimal places in the product: If factor 1 has $m$ decimal places and factor 2 has $n$ decimal places, then the product has $m + n$ decimal places. When the product doesn't have enough digits, insert leading zeros after the decimal point.
Common Questions
How do you place the decimal point when multiplying decimals?
When multiplying decimals, count the total number of decimal places in both factors. Place the decimal point in the product so it has that same total number of decimal places from the right.
What is the rule for decimal point placement in multiplication?
The product of two decimal numbers has as many decimal places as the sum of the decimal places in the two factors. For example, 2.3 x 1.4 has 2 decimal places total, so the product 3.22 has 2 decimal places.
How does dividing decimals affect the decimal point?
When dividing decimals, you can move the decimal point in both the divisor and dividend the same number of places to make the divisor a whole number, then divide normally.
Where is this skill covered in Big Ideas Math Advanced 1?
Decimal point placement rules are taught in Chapter 2: Fractions and Decimals of Big Ideas Math Advanced 1, the Grade 6 math textbook.