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Finding the Fourth Proportional to 139.65, 209.36 and 85.43

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Solution

The fourth proportional to 139.65, 209.36 and 85.43 is: 128.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.65 : 209.36 = 85.43 : x
  2. Step 2: Convert to fraction form
    139.65/209.36 = 85.43/x
  3. Step 3: Cross multiply
    139.65x = 209.36 × 85.43
  4. Step 4: Simplify right side
    139.65x = 17,885.53
  5. Step 5: Solve for x
    x = 17,885.53/139.65
  6. Step 6: Final answer
    x = 128.07

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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.