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Finding the Third Proportional to 20 and 21

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Solution

The third proportional to 20 and 21 is: 22.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    20 : 21 = 21 : x
  2. Step 2: Convert to fraction form
    20/21 = 21/x
  3. Step 3: Cross multiply
    20x = 21 × 21
  4. Step 4: Simplify right side
    20x = 441
  5. Step 5: Solve for x
    x = 441/20
  6. Step 6: Final answer
    x = 22.05

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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.05) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.