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Finding the Fourth Proportional to 91.86, 137.78 and 86.58

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Solution

The fourth proportional to 91.86, 137.78 and 86.58 is: 129.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.86 : 137.78 = 86.58 : x
  2. Step 2: Convert to fraction form
    91.86/137.78 = 86.58/x
  3. Step 3: Cross multiply
    91.86x = 137.78 × 86.58
  4. Step 4: Simplify right side
    91.86x = 11,928.99
  5. Step 5: Solve for x
    x = 11,928.99/91.86
  6. Step 6: Final answer
    x = 129.86

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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.