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Finding the Fourth Proportional to 138.81, 208.35 and 90.75

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Solution

The fourth proportional to 138.81, 208.35 and 90.75 is: 136.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.81 : 208.35 = 90.75 : x
  2. Step 2: Convert to fraction form
    138.81/208.35 = 90.75/x
  3. Step 3: Cross multiply
    138.81x = 208.35 × 90.75
  4. Step 4: Simplify right side
    138.81x = 18,907.76
  5. Step 5: Solve for x
    x = 18,907.76/138.81
  6. Step 6: Final answer
    x = 136.21

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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.