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Finding the Fourth Proportional to 278.79, 418.20 and 86.46

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Solution

The fourth proportional to 278.79, 418.20 and 86.46 is: 129.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    278.79 : 418.20 = 86.46 : x
  2. Step 2: Convert to fraction form
    278.79/418.20 = 86.46/x
  3. Step 3: Cross multiply
    278.79x = 418.20 × 86.46
  4. Step 4: Simplify right side
    278.79x = 36,157.57
  5. Step 5: Solve for x
    x = 36,157.57/278.79
  6. Step 6: Final answer
    x = 129.69

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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.