Solving problems involving Ratio and Proportion

• Ratio


  A relationship between two or more quantities expressed as a fraction
• Proportion


  A relationship between two or more ratios that are equal
• Solving problems involving ratio and proportion

  1. Cross-multiplication

  2. Applying the fundamental law of proportion
• Anne and Argell's heights in photo

  Proportional to their actual heights
• Calculating Argell's actual height

  1. Cross-multiplication: 9x = 10 * 153

  2. x = 170 cm
• Calculating pork needed for 20 people

  1. Cross-multiplication: 4x = 1 * 20

  2. x = 5 kg
• The dimensions are not proportional
• Calculating number of boys

  1. Cross-multiplication: 5x = 4 * 25

  2. x = 20 boys
• Calculating letters in second word

  1. Cross-multiplication: 5x = 3 * 15

  2. x = 9 letters
• Calculating measure of each angle

  1. Sum of angles = 180 degrees

  2. 2x + 3x + 4x = 180

  3. x = 20 degrees

  4. Angles: 40, 60, 80 degrees
• Calculating length of shortest side

  1. Cross-multiplication: 4x + 5x + 6x = 90

  2. x = 6 cm

  3. Shortest side: 24 cm