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Home > CC1 > Chapter 4 > Lesson 4.1.3 > Problem 4-43


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 3 and 10. Then use that number as a common denominator. This table lists multiples of 3 and 10.

  • LCM is 30. Rewrite each fraction to have a denominator of 30 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).