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Finding the Fourth Proportional to 103.85, 155.80 and 85.78

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Solution

The fourth proportional to 103.85, 155.80 and 85.78 is: 128.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    103.85 : 155.80 = 85.78 : x
  2. Step 2: Convert to fraction form
    103.85/155.80 = 85.78/x
  3. Step 3: Cross multiply
    103.85x = 155.80 × 85.78
  4. Step 4: Simplify right side
    103.85x = 13,365.02
  5. Step 5: Solve for x
    x = 13,365.02/103.85
  6. Step 6: Final answer
    x = 128.70

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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.