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Finding the Fourth Proportional to 139.40, 209.15 and 85.33

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Solution

The fourth proportional to 139.40, 209.15 and 85.33 is: 128.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.40 : 209.15 = 85.33 : x
  2. Step 2: Convert to fraction form
    139.40/209.15 = 85.33/x
  3. Step 3: Cross multiply
    139.40x = 209.15 × 85.33
  4. Step 4: Simplify right side
    139.40x = 17,846.46
  5. Step 5: Solve for x
    x = 17,846.46/139.40
  6. Step 6: Final answer
    x = 128.03

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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.