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Finding the Fourth Proportional to 39.80, 54.91 and 31.09

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Solution

The fourth proportional to 39.80, 54.91 and 31.09 is: 42.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    39.80 : 54.91 = 31.09 : x
  2. Step 2: Convert to fraction form
    39.80/54.91 = 31.09/x
  3. Step 3: Cross multiply
    39.80x = 54.91 × 31.09
  4. Step 4: Simplify right side
    39.80x = 1,707.15
  5. Step 5: Solve for x
    x = 1,707.15/39.80
  6. Step 6: Final answer
    x = 42.89

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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.