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Finding the Third Proportional to 21.75 and 39

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Solution

The third proportional to 21.75 and 39 is: 69.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.75 : 39 = 39 : x
  2. Step 2: Convert to fraction form
    21.75/39 = 39/x
  3. Step 3: Cross multiply
    21.75x = 39 × 39
  4. Step 4: Simplify right side
    21.75x = 1,521
  5. Step 5: Solve for x
    x = 1,521/21.75
  6. Step 6: Final answer
    x = 69.93

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Why These Related Problems?

These problems maintain the same ratio (1.79) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.