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Finding the Fourth Proportional to 259.86, 389.72 and 77.20

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Solution

The fourth proportional to 259.86, 389.72 and 77.20 is: 115.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    259.86 : 389.72 = 77.20 : x
  2. Step 2: Convert to fraction form
    259.86/389.72 = 77.20/x
  3. Step 3: Cross multiply
    259.86x = 389.72 × 77.20
  4. Step 4: Simplify right side
    259.86x = 30,086.38
  5. Step 5: Solve for x
    x = 30,086.38/259.86
  6. Step 6: Final answer
    x = 115.78

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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.