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Finding the Fourth Proportional to 39.28, 54.20 and 21.79

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Solution

The fourth proportional to 39.28, 54.20 and 21.79 is: 30.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    39.28 : 54.20 = 21.79 : x
  2. Step 2: Convert to fraction form
    39.28/54.20 = 21.79/x
  3. Step 3: Cross multiply
    39.28x = 54.20 × 21.79
  4. Step 4: Simplify right side
    39.28x = 1,181.05
  5. Step 5: Solve for x
    x = 1,181.05/39.28
  6. Step 6: Final answer
    x = 30.07

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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.