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Finding the Fourth Proportional to 81.33, 121.28 and 78.15

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Solution

The fourth proportional to 81.33, 121.28 and 78.15 is: 116.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.33 : 121.28 = 78.15 : x
  2. Step 2: Convert to fraction form
    81.33/121.28 = 78.15/x
  3. Step 3: Cross multiply
    81.33x = 121.28 × 78.15
  4. Step 4: Simplify right side
    81.33x = 9,478.10
  5. Step 5: Solve for x
    x = 9,478.10/81.33
  6. Step 6: Final answer
    x = 116.54

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.