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Finding the Fourth Proportional to 76.78, 115.10 and 31.15

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Solution

The fourth proportional to 76.78, 115.10 and 31.15 is: 46.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.78 : 115.10 = 31.15 : x
  2. Step 2: Convert to fraction form
    76.78/115.10 = 31.15/x
  3. Step 3: Cross multiply
    76.78x = 115.10 × 31.15
  4. Step 4: Simplify right side
    76.78x = 3,584.63
  5. Step 5: Solve for x
    x = 3,584.63/76.78
  6. Step 6: Final answer
    x = 46.69

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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.