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Finding the Fourth Proportional to 39.87, 55.40 and 39.20

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Solution

The fourth proportional to 39.87, 55.40 and 39.20 is: 54.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    39.87 : 55.40 = 39.20 : x
  2. Step 2: Convert to fraction form
    39.87/55.40 = 39.20/x
  3. Step 3: Cross multiply
    39.87x = 55.40 × 39.20
  4. Step 4: Simplify right side
    39.87x = 2,171.21
  5. Step 5: Solve for x
    x = 2,171.21/39.87
  6. Step 6: Final answer
    x = 54.46

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Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.