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Finding the Fourth Proportional to 138.86, 208.30 and 87.42

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Solution

The fourth proportional to 138.86, 208.30 and 87.42 is: 131.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.86 : 208.30 = 87.42 : x
  2. Step 2: Convert to fraction form
    138.86/208.30 = 87.42/x
  3. Step 3: Cross multiply
    138.86x = 208.30 × 87.42
  4. Step 4: Simplify right side
    138.86x = 18,209.59
  5. Step 5: Solve for x
    x = 18,209.59/138.86
  6. Step 6: Final answer
    x = 131.14

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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.