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Finding the Fourth Proportional to 278.75, 418.17 and 86.42

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Solution

The fourth proportional to 278.75, 418.17 and 86.42 is: 129.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    278.75 : 418.17 = 86.42 : x
  2. Step 2: Convert to fraction form
    278.75/418.17 = 86.42/x
  3. Step 3: Cross multiply
    278.75x = 418.17 × 86.42
  4. Step 4: Simplify right side
    278.75x = 36,138.25
  5. Step 5: Solve for x
    x = 36,138.25/278.75
  6. Step 6: Final answer
    x = 129.64

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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.