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Finding the Fourth Proportional to 258.86, 388.21 and 85.49

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Solution

The fourth proportional to 258.86, 388.21 and 85.49 is: 128.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.86 : 388.21 = 85.49 : x
  2. Step 2: Convert to fraction form
    258.86/388.21 = 85.49/x
  3. Step 3: Cross multiply
    258.86x = 388.21 × 85.49
  4. Step 4: Simplify right side
    258.86x = 33,188.81
  5. Step 5: Solve for x
    x = 33,188.81/258.86
  6. Step 6: Final answer
    x = 128.21

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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.