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Finding the Fourth Proportional to 138.51, 208.17 and 128.79

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Solution

The fourth proportional to 138.51, 208.17 and 128.79 is: 193.56

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.51 : 208.17 = 128.79 : x
  2. Step 2: Convert to fraction form
    138.51/208.17 = 128.79/x
  3. Step 3: Cross multiply
    138.51x = 208.17 × 128.79
  4. Step 4: Simplify right side
    138.51x = 26,810.21
  5. Step 5: Solve for x
    x = 26,810.21/138.51
  6. Step 6: Final answer
    x = 193.56

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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.