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Finding the Fourth Proportional to 91.91, 136.84 and 86.64

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Solution

The fourth proportional to 91.91, 136.84 and 86.64 is: 128.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.91 : 136.84 = 86.64 : x
  2. Step 2: Convert to fraction form
    91.91/136.84 = 86.64/x
  3. Step 3: Cross multiply
    91.91x = 136.84 × 86.64
  4. Step 4: Simplify right side
    91.91x = 11,855.82
  5. Step 5: Solve for x
    x = 11,855.82/91.91
  6. Step 6: Final answer
    x = 128.99

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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.