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Finding the Fourth Proportional to 76.78, 115.12 and 31.11

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Solution

The fourth proportional to 76.78, 115.12 and 31.11 is: 46.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.78 : 115.12 = 31.11 : x
  2. Step 2: Convert to fraction form
    76.78/115.12 = 31.11/x
  3. Step 3: Cross multiply
    76.78x = 115.12 × 31.11
  4. Step 4: Simplify right side
    76.78x = 3,581.38
  5. Step 5: Solve for x
    x = 3,581.38/76.78
  6. Step 6: Final answer
    x = 46.64

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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.