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Finding the Fourth Proportional to 209.40, 314.40 and 128.61

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Solution

The fourth proportional to 209.40, 314.40 and 128.61 is: 193.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.40 : 314.40 = 128.61 : x
  2. Step 2: Convert to fraction form
    209.40/314.40 = 128.61/x
  3. Step 3: Cross multiply
    209.40x = 314.40 × 128.61
  4. Step 4: Simplify right side
    209.40x = 40,434.98
  5. Step 5: Solve for x
    x = 40,434.98/209.40
  6. Step 6: Final answer
    x = 193.10

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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.