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Finding the Fourth Proportional to 138.40, 207.78 and 86.90

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Solution

The fourth proportional to 138.40, 207.78 and 86.90 is: 130.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.40 : 207.78 = 86.90 : x
  2. Step 2: Convert to fraction form
    138.40/207.78 = 86.90/x
  3. Step 3: Cross multiply
    138.40x = 207.78 × 86.90
  4. Step 4: Simplify right side
    138.40x = 18,056.08
  5. Step 5: Solve for x
    x = 18,056.08/138.40
  6. Step 6: Final answer
    x = 130.46

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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.