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Finding the Fourth Proportional to 138.68, 208.14 and 90.70

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Solution

The fourth proportional to 138.68, 208.14 and 90.70 is: 136.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.68 : 208.14 = 90.70 : x
  2. Step 2: Convert to fraction form
    138.68/208.14 = 90.70/x
  3. Step 3: Cross multiply
    138.68x = 208.14 × 90.70
  4. Step 4: Simplify right side
    138.68x = 18,878.30
  5. Step 5: Solve for x
    x = 18,878.30/138.68
  6. Step 6: Final answer
    x = 136.13

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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.