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Finding the Fourth Proportional to 61.71, 85.15 and 39.90

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Solution

The fourth proportional to 61.71, 85.15 and 39.90 is: 55.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    61.71 : 85.15 = 39.90 : x
  2. Step 2: Convert to fraction form
    61.71/85.15 = 39.90/x
  3. Step 3: Cross multiply
    61.71x = 85.15 × 39.90
  4. Step 4: Simplify right side
    61.71x = 3,397.49
  5. Step 5: Solve for x
    x = 3,397.49/61.71
  6. Step 6: Final answer
    x = 55.06

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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.