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Finding the Fourth Proportional to 91.80, 136.95 and 86.72

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Solution

The fourth proportional to 91.80, 136.95 and 86.72 is: 129.37

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.80 : 136.95 = 86.72 : x
  2. Step 2: Convert to fraction form
    91.80/136.95 = 86.72/x
  3. Step 3: Cross multiply
    91.80x = 136.95 × 86.72
  4. Step 4: Simplify right side
    91.80x = 11,876.30
  5. Step 5: Solve for x
    x = 11,876.30/91.80
  6. Step 6: Final answer
    x = 129.37

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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.