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Finding the Fourth Proportional to 81.34, 121.98 and 40.78

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Solution

The fourth proportional to 81.34, 121.98 and 40.78 is: 61.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.34 : 121.98 = 40.78 : x
  2. Step 2: Convert to fraction form
    81.34/121.98 = 40.78/x
  3. Step 3: Cross multiply
    81.34x = 121.98 × 40.78
  4. Step 4: Simplify right side
    81.34x = 4,974.34
  5. Step 5: Solve for x
    x = 4,974.34/81.34
  6. Step 6: Final answer
    x = 61.15

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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.