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Finding the Fourth Proportional to 209.89, 314.64 and 128.55

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Solution

The fourth proportional to 209.89, 314.64 and 128.55 is: 192.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.89 : 314.64 = 128.55 : x
  2. Step 2: Convert to fraction form
    209.89/314.64 = 128.55/x
  3. Step 3: Cross multiply
    209.89x = 314.64 × 128.55
  4. Step 4: Simplify right side
    209.89x = 40,446.97
  5. Step 5: Solve for x
    x = 40,446.97/209.89
  6. Step 6: Final answer
    x = 192.71

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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.