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Finding the Fourth Proportional to 138.58, 207.90 and 77.76

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Solution

The fourth proportional to 138.58, 207.90 and 77.76 is: 116.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.58 : 207.90 = 77.76 : x
  2. Step 2: Convert to fraction form
    138.58/207.90 = 77.76/x
  3. Step 3: Cross multiply
    138.58x = 207.90 × 77.76
  4. Step 4: Simplify right side
    138.58x = 16,166.30
  5. Step 5: Solve for x
    x = 16,166.30/138.58
  6. Step 6: Final answer
    x = 116.66

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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.