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Finding the Fourth Proportional to 109.20, 163.80 and 78.72

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Solution

The fourth proportional to 109.20, 163.80 and 78.72 is: 118.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    109.20 : 163.80 = 78.72 : x
  2. Step 2: Convert to fraction form
    109.20/163.80 = 78.72/x
  3. Step 3: Cross multiply
    109.20x = 163.80 × 78.72
  4. Step 4: Simplify right side
    109.20x = 12,894.34
  5. Step 5: Solve for x
    x = 12,894.34/109.20
  6. Step 6: Final answer
    x = 118.08

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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.