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Finding the Fourth Proportional to 113.78, 170.31 and 81.20

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Solution

The fourth proportional to 113.78, 170.31 and 81.20 is: 121.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    113.78 : 170.31 = 81.20 : x
  2. Step 2: Convert to fraction form
    113.78/170.31 = 81.20/x
  3. Step 3: Cross multiply
    113.78x = 170.31 × 81.20
  4. Step 4: Simplify right side
    113.78x = 13,829.17
  5. Step 5: Solve for x
    x = 13,829.17/113.78
  6. Step 6: Final answer
    x = 121.54

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.