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Finding the Fourth Proportional to 81.38, 112.20 and 56.72

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Solution

The fourth proportional to 81.38, 112.20 and 56.72 is: 78.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.38 : 112.20 = 56.72 : x
  2. Step 2: Convert to fraction form
    81.38/112.20 = 56.72/x
  3. Step 3: Cross multiply
    81.38x = 112.20 × 56.72
  4. Step 4: Simplify right side
    81.38x = 6,363.98
  5. Step 5: Solve for x
    x = 6,363.98/81.38
  6. Step 6: Final answer
    x = 78.20

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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.