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Finding the Fourth Proportional to 81.72, 112.75 and 57.15

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Solution

The fourth proportional to 81.72, 112.75 and 57.15 is: 78.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.72 : 112.75 = 57.15 : x
  2. Step 2: Convert to fraction form
    81.72/112.75 = 57.15/x
  3. Step 3: Cross multiply
    81.72x = 112.75 × 57.15
  4. Step 4: Simplify right side
    81.72x = 6,443.66
  5. Step 5: Solve for x
    x = 6,443.66/81.72
  6. Step 6: Final answer
    x = 78.85

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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.