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Finding the Fourth Proportional to 198.64, 274.12 and 128.78

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Solution

The fourth proportional to 198.64, 274.12 and 128.78 is: 177.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    198.64 : 274.12 = 128.78 : x
  2. Step 2: Convert to fraction form
    198.64/274.12 = 128.78/x
  3. Step 3: Cross multiply
    198.64x = 274.12 × 128.78
  4. Step 4: Simplify right side
    198.64x = 35,299.48
  5. Step 5: Solve for x
    x = 35,299.48/198.64
  6. Step 6: Final answer
    x = 177.71

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.