Multiplying & Dividing Rational #s

Chapter 2 Lesson 4

Multiplying & Dividing Rational Numbers

We follow the same rules as we would if we were multiplying or dividing integers.

If your signs are the same, your answer is positive.

If your signs are different, your answer is negative.

Multiplying & Dividing Decimals

Multiplying Decimals
  • Determine the sign of your answer
  • Remember you do not have to line up your decimal points before multiplying. After going through the steps of multiplication, count the number of spaces after the decimal point and place your decimal that many places from the end. Remember to pay attention to your signs! They make a huge difference!
  • Example: 12.48 After multiplying we can see that there are two spaces after each
X 8.30 decimal. This means we should have four spots after the decimal
1035840 in our answer so it is 103.5840

Dividing Decimals
  • Determine the sign of your answer
  • When dividing decimals, the divisor (number on the outside, what you are dividing by) needs to be a whole number. To make this happen, we move the decimal over until we have a whole number.
  • We must move the decimal in the dividend (number on the inside, what is being divided) over the same number of times, we then bring the decimal straight up into the quotient (answer).
  • We then divide as normal.
Multiplying and Dividing Decimals Video Tutorial

Multiplying and Dividing Fractions

Multiplying Fractions -
  • Determine the sign of your answer
  • Change any improper fractions to mixed numbers
  • Multiply straight across
  • Simplify if possible


Dividing Fractions

  • Determine the sign of your answer
  • Change any improper fractions to mixed numbers
  • Use keep change flip (multiply by the reciprocal) ---> keep the first fraction the same, change your division to multiplication, flip the second fraction so your denominator becomes your numerator and your numerator your denominator
Fractions - Multiplying and Dividing