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Finding the Fourth Proportional to 118.21, 163.20 and 78.90

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Solution

The fourth proportional to 118.21, 163.20 and 78.90 is: 108.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    118.21 : 163.20 = 78.90 : x
  2. Step 2: Convert to fraction form
    118.21/163.20 = 78.90/x
  3. Step 3: Cross multiply
    118.21x = 163.20 × 78.90
  4. Step 4: Simplify right side
    118.21x = 12,875.27
  5. Step 5: Solve for x
    x = 12,875.27/118.21
  6. Step 6: Final answer
    x = 108.92

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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.