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Finding the Fourth Proportional to 122.42, 168.90 and 78.78

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Solution

The fourth proportional to 122.42, 168.90 and 78.78 is: 108.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    122.42 : 168.90 = 78.78 : x
  2. Step 2: Convert to fraction form
    122.42/168.90 = 78.78/x
  3. Step 3: Cross multiply
    122.42x = 168.90 × 78.78
  4. Step 4: Simplify right side
    122.42x = 13,305.77
  5. Step 5: Solve for x
    x = 13,305.77/122.42
  6. Step 6: Final answer
    x = 108.69

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.