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Finding the Fourth Proportional to 91.91, 137.13 and 86.40

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Solution

The fourth proportional to 91.91, 137.13 and 86.40 is: 128.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.91 : 137.13 = 86.40 : x
  2. Step 2: Convert to fraction form
    91.91/137.13 = 86.40/x
  3. Step 3: Cross multiply
    91.91x = 137.13 × 86.40
  4. Step 4: Simplify right side
    91.91x = 11,848.03
  5. Step 5: Solve for x
    x = 11,848.03/91.91
  6. Step 6: Final answer
    x = 128.92

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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.