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Finding the Fourth Proportional to 120.78, 180.36 and 81.96

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Solution

The fourth proportional to 120.78, 180.36 and 81.96 is: 122.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.78 : 180.36 = 81.96 : x
  2. Step 2: Convert to fraction form
    120.78/180.36 = 81.96/x
  3. Step 3: Cross multiply
    120.78x = 180.36 × 81.96
  4. Step 4: Simplify right side
    120.78x = 14,782.31
  5. Step 5: Solve for x
    x = 14,782.31/120.78
  6. Step 6: Final answer
    x = 122.39

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.