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AAAMath: Cross Multiplication to Solve Proportions


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Activity Description


Solving Proportions by Cross Multipying
Source: Cross Multiplication to Solve Proportions Practice page (License: Protected by Copyright (c) [i.e. screenshot])
This activity gives students the needed practice to reinforce classroom instruction on using proportions and cross-multiplying to solve problems. This lesson provides students with a short review of the lesson, Interactive Practice, and Play, which includes timed games.


  1. Check that the site is not blocked by your school.
  2. Preview the lesson, which is found under ratios.
  3. Try some of the exercises to check the difficulty level.
  4. Review the lesson and practice activities.

Teacher Tips

There are numerous short lessons on ratios. The “Uses of the Percent Ratio” lessons have several different applications of ratios. Depending on the available class time, you can present several lessons during a class period.

More Ways

To use this site in Spanish, just click on Spanish Version of AAAMath at the bottom of the yellow left side list.

Program Areas

  • ASE: High School Equivalency Preparation
  • ABE: Adult Basic Education
  • ASE: High School Diploma
  • CTE: Career Technical Education


  • High

Lesson Plan


Begin with a review of previous content related to proportions and percentages.



Introduce the lesson and discuss the importance of being able to solve proportion problems. Try to use real-life applications.

  • If the formula calls for 3 ml to be dissolved in 75 ml of water, how much is needed for 500 ml of water?
  • If a garment is 30% off, how much will you pay for one that costs $25.00?
  • Give the students a percentage problem and ask them how they would solve the problem.
  • Give students time to explore different methods of finding the solution. This works well in small groups. Have the groups share their findings.
  • Guide instruction to clarify any misconceptions and direct learning.
  1. Use Interactive Practice to generate problems.
  2. If you have access to a computer lab, give students time to practice their skills. If students have Internet access at home, encourage students to practice their skills at home.
  3. The next day you can discuss any problems students had with the problems and reteach as necessary.

Check for understanding by giving a short formative quiz.

Reteach concepts as needed

Engagement Extension

Divide students into small groups to explore different ways to use proportions in their lives then have the groups share with the class. As different groups share, write their answers on the board.



  • Math
    • Algebra
    • Conversions
    • Proportions
  • Science
    • Chemistry
    • Physics

CTE Sectors

  • Building and Construction Trades
  • Business and Finance
  • Engineering and Architecture
  • Health Science and Medical Technology

CTE Anchor Standards

  • Anchor Standard 5: Problem Solving and Critical Thinking - Writing Standard: Conduct short as well as more sustained research projects to answer a question (including a self-generated question) or solve a problem, narrow or broaden the inquiry when appropriate, and synthesize multiple sources on the subject, demonstrating understanding of the subject under investigation.
  • Anchor Standard 11: Demonstration and Application - Demonstrate and apply the knowledge and skills contained in the industry-sector anchor standards, pathway standards, and performance indicators in classroom, laboratory, and workplace settings, and the career technical student organization.


  • Ratios and Proportional Relationships
    • 6.RP.1-2 - Understand ratio concepts and use ratio reasoning to solve problems.


math, ratio, ratios, AAA, AAAMath, cross, equations, multipying, proportion


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OTAN activities are funded by contract CN220124 from the Adult Education Office, in the Career & College Transition Division, California Department of Education, with funds provided through Federal P.L., 105-220, Section 223. However, OTAN content does not necessarily reflect the position of that department or the U.S. Department of Education.