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Finding the Fourth Proportional to 138.60, 207.11 and 99.90

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Solution

The fourth proportional to 138.60, 207.11 and 99.90 is: 149.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.60 : 207.11 = 99.90 : x
  2. Step 2: Convert to fraction form
    138.60/207.11 = 99.90/x
  3. Step 3: Cross multiply
    138.60x = 207.11 × 99.90
  4. Step 4: Simplify right side
    138.60x = 20,689.79
  5. Step 5: Solve for x
    x = 20,689.79/138.60
  6. Step 6: Final answer
    x = 149.28

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.