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Finding the Fourth Proportional to 139.26, 208.70 and 85.20

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Solution

The fourth proportional to 139.26, 208.70 and 85.20 is: 127.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.26 : 208.70 = 85.20 : x
  2. Step 2: Convert to fraction form
    139.26/208.70 = 85.20/x
  3. Step 3: Cross multiply
    139.26x = 208.70 × 85.20
  4. Step 4: Simplify right side
    139.26x = 17,781.24
  5. Step 5: Solve for x
    x = 17,781.24/139.26
  6. Step 6: Final answer
    x = 127.68

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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.