Multiplying Decimals. Dividing Decimals. Quick method: use Long Division without the decimal point, then re-insert the decimal point in the answer. Dividing a Decimal Number by a Whole Number To divide a decimal number by a whole number: Use Division or Long Division (ignoring the decimal point) Then put the decimal point in the same spot as the dividend (the number being divided) Example: Divide 9.1 by 7 Ignore the decimal point and use Long Division: Put the decimal point in the answer directly above the decimal point in the dividend: The answer is 1.3 Dividing by a Decimal Number But what if you want to divide by a Decimal Number? The trick is to convert the number you are dividing by to a whole number first, by shifting the decimal point of both numbers to the right: Now you are dividing by a whole number, and can continue as normal. It is safe to do this if you remember to shift the decimal point of both numbers the same number of places. Example: Divide 6.4 by 0.4 And the answer is: You can see for yourself how many 0.4s make 6.4:
2 + 1 Math Rocks! The Decimal Song. Dividing Decimals. Multiplying Decimals. Multiplying and Dividing with Decimals. Multiplying Decimals Suppose you're multiplying a decimal by a whole number, say This is the same as adding the decimal three times: . You can think of it as follows: If three friends each have 12 cents, together, they have a total of 36 cents. It's a bit trickier when both numbers are decimals. . Remember that decimals are just another way of writing fractions that have powers of 10 in the denominator. As Then you would multiply numerators and denominators to get . Of course, you don't have to convert to fraction notation every time. Standard Algorithm for Multiplying Decimals First just multiply the numbers as if they were whole numbers.
Then count the total number of places to the right of the decimal point in BOTH numbers you're multiplying. Example: Multiply 3.1 × 5.06. Step 1: Multiply the numbers, ignoring the decimal point. Step 2: In 3.1, there is 1 place to the right of the decimal point. Why does this work? Dividing with Decimals Dividing with decimals is a bit more difficult. Divide.