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Finding the Fourth Proportional to 91.78, 127.31 and 86.92

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Solution

The fourth proportional to 91.78, 127.31 and 86.92 is: 120.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.78 : 127.31 = 86.92 : x
  2. Step 2: Convert to fraction form
    91.78/127.31 = 86.92/x
  3. Step 3: Cross multiply
    91.78x = 127.31 × 86.92
  4. Step 4: Simplify right side
    91.78x = 11,065.79
  5. Step 5: Solve for x
    x = 11,065.79/91.78
  6. Step 6: Final answer
    x = 120.57

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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.