Ratio: numerical representation of a comparison (ex. 3:2 “three to two”)

    15 teachers : 120 students --> 15 : 120 --> 15/120 = 1/8 --> 1 teacher : 8 students

SAMPLE PRACTICE QUESTIONS FOR RATIOS

1. What is the number of boys in a class of 20 if the ratio of boys to girls is 3:2?

      Solution
      A) # boys = b; # girls = (20 - b)
          b : 20 - b = 3 : 2 --> b / (20 - b) = 3 / 2

      B) Cross-Multiply
          3(20 – b) = 2b
          60 – 3b = 2b
          60 = 5b
          12 = b

2. The ratio of apples to oranges is 4:3 and the ratio of pears to oranges to is 7:6. What is the ratio of apples to pears?

     Solution
    A) apples to oranges = 4:3
        pears to oranges = 7:6
        The ratios have oranges in common. So you must make the number of oranges the same.

    B) apples to oranges = (4:3) × 2 = 8:6
        pears to oranges = 7:6
        Now you can create a new ratio by eliminating oranges. The ratio of apples to pears = 8:7

SAT Math: Ratios

Lesson Includes:

— Math Terms for Ratios

—Sample Practice Questions

— Practice Questions

Math

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SAT Writing

SAT Vocabulary

RATIOS REVIEW QUIZ

 

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