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Finding the Fourth Proportional to 139.68, 193.20 and 128.88

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Solution

The fourth proportional to 139.68, 193.20 and 128.88 is: 178.26

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.68 : 193.20 = 128.88 : x
  2. Step 2: Convert to fraction form
    139.68/193.20 = 128.88/x
  3. Step 3: Cross multiply
    139.68x = 193.20 × 128.88
  4. Step 4: Simplify right side
    139.68x = 24,899.62
  5. Step 5: Solve for x
    x = 24,899.62/139.68
  6. Step 6: Final answer
    x = 178.26

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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.