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Finding the Fourth Proportional to 122.38, 168.72 and 78.64

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Solution

The fourth proportional to 122.38, 168.72 and 78.64 is: 108.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    122.38 : 168.72 = 78.64 : x
  2. Step 2: Convert to fraction form
    122.38/168.72 = 78.64/x
  3. Step 3: Cross multiply
    122.38x = 168.72 × 78.64
  4. Step 4: Simplify right side
    122.38x = 13,268.14
  5. Step 5: Solve for x
    x = 13,268.14/122.38
  6. Step 6: Final answer
    x = 108.42

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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.