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Finding the Fourth Proportional to 91.58, 136.56 and 86.78

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Solution

The fourth proportional to 91.58, 136.56 and 86.78 is: 129.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.58 : 136.56 = 86.78 : x
  2. Step 2: Convert to fraction form
    91.58/136.56 = 86.78/x
  3. Step 3: Cross multiply
    91.58x = 136.56 × 86.78
  4. Step 4: Simplify right side
    91.58x = 11,850.68
  5. Step 5: Solve for x
    x = 11,850.68/91.58
  6. Step 6: Final answer
    x = 129.40

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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.