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Finding the Fourth Proportional to 39.78, 54.85 and 31.58

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Solution

The fourth proportional to 39.78, 54.85 and 31.58 is: 43.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    39.78 : 54.85 = 31.58 : x
  2. Step 2: Convert to fraction form
    39.78/54.85 = 31.58/x
  3. Step 3: Cross multiply
    39.78x = 54.85 × 31.58
  4. Step 4: Simplify right side
    39.78x = 1,732.22
  5. Step 5: Solve for x
    x = 1,732.22/39.78
  6. Step 6: Final answer
    x = 43.55

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.