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Finding the Fourth Proportional to 80.90, 120.74 and 78.20

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Solution

The fourth proportional to 80.90, 120.74 and 78.20 is: 116.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    80.90 : 120.74 = 78.20 : x
  2. Step 2: Convert to fraction form
    80.90/120.74 = 78.20/x
  3. Step 3: Cross multiply
    80.90x = 120.74 × 78.20
  4. Step 4: Simplify right side
    80.90x = 9,441.87
  5. Step 5: Solve for x
    x = 9,441.87/80.90
  6. Step 6: Final answer
    x = 116.71

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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.