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Finding the Third Proportional to 78 and 138.75

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Solution

The third proportional to 78 and 138.75 is: 246.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    78 : 138.75 = 138.75 : x
  2. Step 2: Convert to fraction form
    78/138.75 = 138.75/x
  3. Step 3: Cross multiply
    78x = 138.75 × 138.75
  4. Step 4: Simplify right side
    78x = 19,251.56
  5. Step 5: Solve for x
    x = 19,251.56/78
  6. Step 6: Final answer
    x = 246.81

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Why These Related Problems?

These problems maintain the same ratio (1.78) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.