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Finding the Fourth Proportional to 31.78, 43.91 and 28.74

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Solution

The fourth proportional to 31.78, 43.91 and 28.74 is: 39.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.78 : 43.91 = 28.74 : x
  2. Step 2: Convert to fraction form
    31.78/43.91 = 28.74/x
  3. Step 3: Cross multiply
    31.78x = 43.91 × 28.74
  4. Step 4: Simplify right side
    31.78x = 1,261.97
  5. Step 5: Solve for x
    x = 1,261.97/31.78
  6. Step 6: Final answer
    x = 39.71

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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.