Unit 10

Combined Operations with Common Fractions

Basic Principles of Combined Operations with Common Fractions

• Follow the rules for addition, subtraction, multiplication, and division of common fractions to solve problems that combine operations with common fractions.

• The first step in solving these problems is determining which operations are needed and in what order.

Basic Principles of Combined Operations with Common Fractions

• Convert everything to the same units.

• Convert all fractions used in addition or subtraction to the lowest common denominators.

• Do the math necessary to solve the problem.

Combined Operations with Common Fractions

• Example: Solve

– Solve the first half of the problem:

Combined Operations with Common Fractions

• Solve within parentheses, then add:

• Remember to reduce the answer to the lowest terms.

Practical Problem

• A patient is taking 2 1/2 milligrams (mg) of Valium tid (three times a day).

• If each Valium tablet contains 5 mg, how many tablets does the patient take every day?

Practical Problem

• Set up the problem and solve within parentheses first:

• The patient takes 1 1/2 tablets each day.