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Finding the Fourth Proportional to 138, 207.12 and 84

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Solution

The fourth proportional to 138, 207.12 and 84 is: 126.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    138 : 207.12 = 84 : x
  2. Step 2: Convert to fraction form
    138/207.12 = 84/x
  3. Step 3: Cross multiply
    138x = 207.12 × 84
  4. Step 4: Simplify right side
    138x = 17,398.08
  5. Step 5: Solve for x
    x = 17,398.08/138
  6. Step 6: Final answer
    x = 126.07

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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.