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Finding the Third Proportional to 20 and 42

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Solution

The third proportional to 20 and 42 is: 88.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    20 : 42 = 42 : x
  2. Step 2: Convert to fraction form
    20/42 = 42/x
  3. Step 3: Cross multiply
    20x = 42 × 42
  4. Step 4: Simplify right side
    20x = 1,764
  5. Step 5: Solve for x
    x = 1,764/20
  6. Step 6: Final answer
    x = 88.20

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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (2.10) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.