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Finding the Fourth Proportional to 103.78, 155.70 and 76.78

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Solution

The fourth proportional to 103.78, 155.70 and 76.78 is: 115.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    103.78 : 155.70 = 76.78 : x
  2. Step 2: Convert to fraction form
    103.78/155.70 = 76.78/x
  3. Step 3: Cross multiply
    103.78x = 155.70 × 76.78
  4. Step 4: Simplify right side
    103.78x = 11,954.65
  5. Step 5: Solve for x
    x = 11,954.65/103.78
  6. Step 6: Final answer
    x = 115.19

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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.