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Finding the Fourth Proportional to 258.51, 387.69 and 85.15

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Solution

The fourth proportional to 258.51, 387.69 and 85.15 is: 127.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.51 : 387.69 = 85.15 : x
  2. Step 2: Convert to fraction form
    258.51/387.69 = 85.15/x
  3. Step 3: Cross multiply
    258.51x = 387.69 × 85.15
  4. Step 4: Simplify right side
    258.51x = 33,011.15
  5. Step 5: Solve for x
    x = 33,011.15/258.51
  6. Step 6: Final answer
    x = 127.70

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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.