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Finding the Fourth Proportional to 39.72, 54.80 and 28.78

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Solution

The fourth proportional to 39.72, 54.80 and 28.78 is: 39.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    39.72 : 54.80 = 28.78 : x
  2. Step 2: Convert to fraction form
    39.72/54.80 = 28.78/x
  3. Step 3: Cross multiply
    39.72x = 54.80 × 28.78
  4. Step 4: Simplify right side
    39.72x = 1,577.14
  5. Step 5: Solve for x
    x = 1,577.14/39.72
  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.