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Finding the Third Proportional to 11 and 21

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Solution

The third proportional to 11 and 21 is: 40.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    11 : 21 = 21 : x
  2. Step 2: Convert to fraction form
    11/21 = 21/x
  3. Step 3: Cross multiply
    11x = 21 × 21
  4. Step 4: Simplify right side
    11x = 441
  5. Step 5: Solve for x
    x = 441/11
  6. Step 6: Final answer
    x = 40.09

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Why These Related Problems?

These problems maintain the same ratio (1.91) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.