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Finding the Fourth Proportional to 120.78, 180.90 and 72.54

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Solution

The fourth proportional to 120.78, 180.90 and 72.54 is: 108.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.78 : 180.90 = 72.54 : x
  2. Step 2: Convert to fraction form
    120.78/180.90 = 72.54/x
  3. Step 3: Cross multiply
    120.78x = 180.90 × 72.54
  4. Step 4: Simplify right side
    120.78x = 13,122.49
  5. Step 5: Solve for x
    x = 13,122.49/120.78
  6. Step 6: Final answer
    x = 108.65

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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.