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Finding the Fourth Proportional to 312.78, 469.14 and 81.66

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Solution

The fourth proportional to 312.78, 469.14 and 81.66 is: 122.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    312.78 : 469.14 = 81.66 : x
  2. Step 2: Convert to fraction form
    312.78/469.14 = 81.66/x
  3. Step 3: Cross multiply
    312.78x = 469.14 × 81.66
  4. Step 4: Simplify right side
    312.78x = 38,309.97
  5. Step 5: Solve for x
    x = 38,309.97/312.78
  6. Step 6: Final answer
    x = 122.48

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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.