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Finding the Fourth Proportional to 76.78, 115.08 and 64.90

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Solution

The fourth proportional to 76.78, 115.08 and 64.90 is: 97.27

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.78 : 115.08 = 64.90 : x
  2. Step 2: Convert to fraction form
    76.78/115.08 = 64.90/x
  3. Step 3: Cross multiply
    76.78x = 115.08 × 64.90
  4. Step 4: Simplify right side
    76.78x = 7,468.69
  5. Step 5: Solve for x
    x = 7,468.69/76.78
  6. Step 6: Final answer
    x = 97.27

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.