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Finding the Fourth Proportional to 76.90, 115.31 and 31.20

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Solution

The fourth proportional to 76.90, 115.31 and 31.20 is: 46.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.90 : 115.31 = 31.20 : x
  2. Step 2: Convert to fraction form
    76.90/115.31 = 31.20/x
  3. Step 3: Cross multiply
    76.90x = 115.31 × 31.20
  4. Step 4: Simplify right side
    76.90x = 3,597.08
  5. Step 5: Solve for x
    x = 3,597.08/76.90
  6. Step 6: Final answer
    x = 46.78

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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.