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Finding the Fourth Proportional to 139.70, 209.10 and 128.90

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Solution

The fourth proportional to 139.70, 209.10 and 128.90 is: 192.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.70 : 209.10 = 128.90 : x
  2. Step 2: Convert to fraction form
    139.70/209.10 = 128.90/x
  3. Step 3: Cross multiply
    139.70x = 209.10 × 128.90
  4. Step 4: Simplify right side
    139.70x = 26,952.99
  5. Step 5: Solve for x
    x = 26,952.99/139.70
  6. Step 6: Final answer
    x = 192.93

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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.