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Finding the Fourth Proportional to 138.65, 208.16 and 90.20

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Solution

The fourth proportional to 138.65, 208.16 and 90.20 is: 135.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.65 : 208.16 = 90.20 : x
  2. Step 2: Convert to fraction form
    138.65/208.16 = 90.20/x
  3. Step 3: Cross multiply
    138.65x = 208.16 × 90.20
  4. Step 4: Simplify right side
    138.65x = 18,774.54
  5. Step 5: Solve for x
    x = 18,774.54/138.65
  6. Step 6: Final answer
    x = 135.41

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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.