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Finding the Fourth Proportional to 258.96, 388.20 and 128.88

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Solution

The fourth proportional to 258.96, 388.20 and 128.88 is: 193.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.96 : 388.20 = 128.88 : x
  2. Step 2: Convert to fraction form
    258.96/388.20 = 128.88/x
  3. Step 3: Cross multiply
    258.96x = 388.20 × 128.88
  4. Step 4: Simplify right side
    258.96x = 50,031.22
  5. Step 5: Solve for x
    x = 50,031.22/258.96
  6. Step 6: Final answer
    x = 193.20

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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.