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Finding the Fourth Proportional to 278.11, 417.21 and 85.69

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Solution

The fourth proportional to 278.11, 417.21 and 85.69 is: 128.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    278.11 : 417.21 = 85.69 : x
  2. Step 2: Convert to fraction form
    278.11/417.21 = 85.69/x
  3. Step 3: Cross multiply
    278.11x = 417.21 × 85.69
  4. Step 4: Simplify right side
    278.11x = 35,749.68
  5. Step 5: Solve for x
    x = 35,749.68/278.11
  6. Step 6: Final answer
    x = 128.55

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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.