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Finding the Fourth Proportional to 258.40, 387.69 and 136.90

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Solution

The fourth proportional to 258.40, 387.69 and 136.90 is: 205.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.40 : 387.69 = 136.90 : x
  2. Step 2: Convert to fraction form
    258.40/387.69 = 136.90/x
  3. Step 3: Cross multiply
    258.40x = 387.69 × 136.90
  4. Step 4: Simplify right side
    258.40x = 53,074.76
  5. Step 5: Solve for x
    x = 53,074.76/258.40
  6. Step 6: Final answer
    x = 205.40

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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.