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Finding the Fourth Proportional to 259.15, 388.78 and 85.87

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Solution

The fourth proportional to 259.15, 388.78 and 85.87 is: 128.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    259.15 : 388.78 = 85.87 : x
  2. Step 2: Convert to fraction form
    259.15/388.78 = 85.87/x
  3. Step 3: Cross multiply
    259.15x = 388.78 × 85.87
  4. Step 4: Simplify right side
    259.15x = 33,382.17
  5. Step 5: Solve for x
    x = 33,382.17/259.15
  6. Step 6: Final answer
    x = 128.82

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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.