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Finding the Fourth Proportional to 81.15, 112.74 and 80.40

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Solution

The fourth proportional to 81.15, 112.74 and 80.40 is: 111.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.15 : 112.74 = 80.40 : x
  2. Step 2: Convert to fraction form
    81.15/112.74 = 80.40/x
  3. Step 3: Cross multiply
    81.15x = 112.74 × 80.40
  4. Step 4: Simplify right side
    81.15x = 9,064.30
  5. Step 5: Solve for x
    x = 9,064.30/81.15
  6. Step 6: Final answer
    x = 111.70

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Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.