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Finding the Fourth Proportional to 258.71, 388.11 and 85.40

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Solution

The fourth proportional to 258.71, 388.11 and 85.40 is: 128.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.71 : 388.11 = 85.40 : x
  2. Step 2: Convert to fraction form
    258.71/388.11 = 85.40/x
  3. Step 3: Cross multiply
    258.71x = 388.11 × 85.40
  4. Step 4: Simplify right side
    258.71x = 33,142.65
  5. Step 5: Solve for x
    x = 33,142.65/258.71
  6. Step 6: Final answer
    x = 128.11

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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.