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Finding the Fourth Proportional to 61.90, 92.85 and 21.31

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Solution

The fourth proportional to 61.90, 92.85 and 21.31 is: 31.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    61.90 : 92.85 = 21.31 : x
  2. Step 2: Convert to fraction form
    61.90/92.85 = 21.31/x
  3. Step 3: Cross multiply
    61.90x = 92.85 × 21.31
  4. Step 4: Simplify right side
    61.90x = 1,978.17
  5. Step 5: Solve for x
    x = 1,978.17/61.90
  6. Step 6: Final answer
    x = 31.96

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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.