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Finding the Fourth Proportional to 137.72, 206.40 and 76.88

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Solution

The fourth proportional to 137.72, 206.40 and 76.88 is: 115.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    137.72 : 206.40 = 76.88 : x
  2. Step 2: Convert to fraction form
    137.72/206.40 = 76.88/x
  3. Step 3: Cross multiply
    137.72x = 206.40 × 76.88
  4. Step 4: Simplify right side
    137.72x = 15,868.03
  5. Step 5: Solve for x
    x = 15,868.03/137.72
  6. Step 6: Final answer
    x = 115.22

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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.