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Finding the Fourth Proportional to 138.13, 206.70 and 86.80

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Solution

The fourth proportional to 138.13, 206.70 and 86.80 is: 129.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.13 : 206.70 = 86.80 : x
  2. Step 2: Convert to fraction form
    138.13/206.70 = 86.80/x
  3. Step 3: Cross multiply
    138.13x = 206.70 × 86.80
  4. Step 4: Simplify right side
    138.13x = 17,941.56
  5. Step 5: Solve for x
    x = 17,941.56/138.13
  6. Step 6: Final answer
    x = 129.89

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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.