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Finding the Fourth Proportional to 66.90, 100.40 and 39.86

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Solution

The fourth proportional to 66.90, 100.40 and 39.86 is: 59.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    66.90 : 100.40 = 39.86 : x
  2. Step 2: Convert to fraction form
    66.90/100.40 = 39.86/x
  3. Step 3: Cross multiply
    66.90x = 100.40 × 39.86
  4. Step 4: Simplify right side
    66.90x = 4,001.94
  5. Step 5: Solve for x
    x = 4,001.94/66.90
  6. Step 6: Final answer
    x = 59.82

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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.