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Finding the Fourth Proportional to 91.78, 137.76 and 86.02

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Solution

The fourth proportional to 91.78, 137.76 and 86.02 is: 129.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.78 : 137.76 = 86.02 : x
  2. Step 2: Convert to fraction form
    91.78/137.76 = 86.02/x
  3. Step 3: Cross multiply
    91.78x = 137.76 × 86.02
  4. Step 4: Simplify right side
    91.78x = 11,850.12
  5. Step 5: Solve for x
    x = 11,850.12/91.78
  6. Step 6: Final answer
    x = 129.11

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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.