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Finding the Fourth Proportional to 139.02, 208.17 and 90.78

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Solution

The fourth proportional to 139.02, 208.17 and 90.78 is: 135.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.02 : 208.17 = 90.78 : x
  2. Step 2: Convert to fraction form
    139.02/208.17 = 90.78/x
  3. Step 3: Cross multiply
    139.02x = 208.17 × 90.78
  4. Step 4: Simplify right side
    139.02x = 18,897.67
  5. Step 5: Solve for x
    x = 18,897.67/139.02
  6. Step 6: Final answer
    x = 135.93

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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.