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Finding the Fourth Proportional to 139.28, 208.68 and 85.22

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Solution

The fourth proportional to 139.28, 208.68 and 85.22 is: 127.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.28 : 208.68 = 85.22 : x
  2. Step 2: Convert to fraction form
    139.28/208.68 = 85.22/x
  3. Step 3: Cross multiply
    139.28x = 208.68 × 85.22
  4. Step 4: Simplify right side
    139.28x = 17,783.71
  5. Step 5: Solve for x
    x = 17,783.71/139.28
  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.