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Finding the Fourth Proportional to 137.56, 206.40 and 76.78

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Solution

The fourth proportional to 137.56, 206.40 and 76.78 is: 115.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    137.56 : 206.40 = 76.78 : x
  2. Step 2: Convert to fraction form
    137.56/206.40 = 76.78/x
  3. Step 3: Cross multiply
    137.56x = 206.40 × 76.78
  4. Step 4: Simplify right side
    137.56x = 15,847.39
  5. Step 5: Solve for x
    x = 15,847.39/137.56
  6. Step 6: Final answer
    x = 115.20

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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.