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Finding the Fourth Proportional to 258.90, 388.21 and 128.63

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Solution

The fourth proportional to 258.90, 388.21 and 128.63 is: 192.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.90 : 388.21 = 128.63 : x
  2. Step 2: Convert to fraction form
    258.90/388.21 = 128.63/x
  3. Step 3: Cross multiply
    258.90x = 388.21 × 128.63
  4. Step 4: Simplify right side
    258.90x = 49,936.10
  5. Step 5: Solve for x
    x = 49,936.10/258.90
  6. Step 6: Final answer
    x = 192.88

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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.