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Finding the Fourth Proportional to 120.78, 180.88 and 86.56

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Solution

The fourth proportional to 120.78, 180.88 and 86.56 is: 129.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.78 : 180.88 = 86.56 : x
  2. Step 2: Convert to fraction form
    120.78/180.88 = 86.56/x
  3. Step 3: Cross multiply
    120.78x = 180.88 × 86.56
  4. Step 4: Simplify right side
    120.78x = 15,656.97
  5. Step 5: Solve for x
    x = 15,656.97/120.78
  6. Step 6: Final answer
    x = 129.63

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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.