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Finding the Fourth Proportional to 209.78, 314.46 and 87.91

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Solution

The fourth proportional to 209.78, 314.46 and 87.91 is: 131.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.78 : 314.46 = 87.91 : x
  2. Step 2: Convert to fraction form
    209.78/314.46 = 87.91/x
  3. Step 3: Cross multiply
    209.78x = 314.46 × 87.91
  4. Step 4: Simplify right side
    209.78x = 27,644.18
  5. Step 5: Solve for x
    x = 27,644.18/209.78
  6. Step 6: Final answer
    x = 131.78

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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.