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Finding the Fourth Proportional to 81.78, 112.76 and 57.21

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Solution

The fourth proportional to 81.78, 112.76 and 57.21 is: 78.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.78 : 112.76 = 57.21 : x
  2. Step 2: Convert to fraction form
    81.78/112.76 = 57.21/x
  3. Step 3: Cross multiply
    81.78x = 112.76 × 57.21
  4. Step 4: Simplify right side
    81.78x = 6,450.71
  5. Step 5: Solve for x
    x = 6,450.71/81.78
  6. Step 6: Final answer
    x = 78.88

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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.