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Finding the Fourth Proportional to 138.02, 206.58 and 86.72

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Solution

The fourth proportional to 138.02, 206.58 and 86.72 is: 129.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.02 : 206.58 = 86.72 : x
  2. Step 2: Convert to fraction form
    138.02/206.58 = 86.72/x
  3. Step 3: Cross multiply
    138.02x = 206.58 × 86.72
  4. Step 4: Simplify right side
    138.02x = 17,914.62
  5. Step 5: Solve for x
    x = 17,914.62/138.02
  6. Step 6: Final answer
    x = 129.80

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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.