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Finding the Fourth Proportional to 81.78, 113.40 and 80.30

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Solution

The fourth proportional to 81.78, 113.40 and 80.30 is: 111.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.78 : 113.40 = 80.30 : x
  2. Step 2: Convert to fraction form
    81.78/113.40 = 80.30/x
  3. Step 3: Cross multiply
    81.78x = 113.40 × 80.30
  4. Step 4: Simplify right side
    81.78x = 9,106.02
  5. Step 5: Solve for x
    x = 9,106.02/81.78
  6. Step 6: Final answer
    x = 111.35

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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.