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Finding the Third Proportional to 78 and 121.31

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Solution

The third proportional to 78 and 121.31 is: 188.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    78 : 121.31 = 121.31 : x
  2. Step 2: Convert to fraction form
    78/121.31 = 121.31/x
  3. Step 3: Cross multiply
    78x = 121.31 × 121.31
  4. Step 4: Simplify right side
    78x = 14,716.72
  5. Step 5: Solve for x
    x = 14,716.72/78
  6. Step 6: Final answer
    x = 188.68

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Why These Related Problems?

These problems maintain the same ratio (1.56) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.