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Finding the Fourth Proportional to 39.85, 59.78 and 21.80

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Solution

The fourth proportional to 39.85, 59.78 and 21.80 is: 32.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    39.85 : 59.78 = 21.80 : x
  2. Step 2: Convert to fraction form
    39.85/59.78 = 21.80/x
  3. Step 3: Cross multiply
    39.85x = 59.78 × 21.80
  4. Step 4: Simplify right side
    39.85x = 1,303.20
  5. Step 5: Solve for x
    x = 1,303.20/39.85
  6. Step 6: Final answer
    x = 32.71

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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.