CPM Homework Banner

Home > MC1 > Chapter 8 > Lesson 8.2.3 > Problem 8-56


Find each sum or difference without a calculator.

Compute without a calculator


  • Find a common denominator.

  • To add the fractions together, start by finding the least common multiple of and . Then use that number as a common denominator. This table lists multiples of and .

  • LCM is . Rewrite each fraction to have a denominator of by using Giant Ones, as shown below. Can you add the fractions now?
    Giant One: 3 divided by 3A Giant One: 10 divided by 10


    Whenever adding or subtracting decimals, be sure to line up the decimal points! It may help to write this problem like this:

    Also, remember that the decimal point will fall in the same place in your answer.


    . Rewrite  as a fraction greater than one. Then follow the example in Part (a).