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Finding the Fourth Proportional to 39.78, 59.60 and 21.69

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Solution

The fourth proportional to 39.78, 59.60 and 21.69 is: 32.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    39.78 : 59.60 = 21.69 : x
  2. Step 2: Convert to fraction form
    39.78/59.60 = 21.69/x
  3. Step 3: Cross multiply
    39.78x = 59.60 × 21.69
  4. Step 4: Simplify right side
    39.78x = 1,292.72
  5. Step 5: Solve for x
    x = 1,292.72/39.78
  6. Step 6: Final answer
    x = 32.50

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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.