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Finding the Fourth Proportional to 39.86, 59.78 and 20.61

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Solution

The fourth proportional to 39.86, 59.78 and 20.61 is: 30.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    39.86 : 59.78 = 20.61 : x
  2. Step 2: Convert to fraction form
    39.86/59.78 = 20.61/x
  3. Step 3: Cross multiply
    39.86x = 59.78 × 20.61
  4. Step 4: Simplify right side
    39.86x = 1,232.07
  5. Step 5: Solve for x
    x = 1,232.07/39.86
  6. Step 6: Final answer
    x = 30.91

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.