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Finding the Fourth Proportional to 137.91, 206.79 and 86.40

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Solution

The fourth proportional to 137.91, 206.79 and 86.40 is: 129.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    137.91 : 206.79 = 86.40 : x
  2. Step 2: Convert to fraction form
    137.91/206.79 = 86.40/x
  3. Step 3: Cross multiply
    137.91x = 206.79 × 86.40
  4. Step 4: Simplify right side
    137.91x = 17,866.66
  5. Step 5: Solve for x
    x = 17,866.66/137.91
  6. Step 6: Final answer
    x = 129.55

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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.