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Finding the Fourth Proportional to 81.61, 112.45 and 77.21

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Solution

The fourth proportional to 81.61, 112.45 and 77.21 is: 106.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.61 : 112.45 = 77.21 : x
  2. Step 2: Convert to fraction form
    81.61/112.45 = 77.21/x
  3. Step 3: Cross multiply
    81.61x = 112.45 × 77.21
  4. Step 4: Simplify right side
    81.61x = 8,682.26
  5. Step 5: Solve for x
    x = 8,682.26/81.61
  6. Step 6: Final answer
    x = 106.39

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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.