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Finding the Fourth Proportional to 109.42, 163.78 and 78.64

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Solution

The fourth proportional to 109.42, 163.78 and 78.64 is: 117.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    109.42 : 163.78 = 78.64 : x
  2. Step 2: Convert to fraction form
    109.42/163.78 = 78.64/x
  3. Step 3: Cross multiply
    109.42x = 163.78 × 78.64
  4. Step 4: Simplify right side
    109.42x = 12,879.66
  5. Step 5: Solve for x
    x = 12,879.66/109.42
  6. Step 6: Final answer
    x = 117.71

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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.