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Finding the Fourth Proportional to 87.80, 120.90 and 79.70

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Solution

The fourth proportional to 87.80, 120.90 and 79.70 is: 109.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.80 : 120.90 = 79.70 : x
  2. Step 2: Convert to fraction form
    87.80/120.90 = 79.70/x
  3. Step 3: Cross multiply
    87.80x = 120.90 × 79.70
  4. Step 4: Simplify right side
    87.80x = 9,635.73
  5. Step 5: Solve for x
    x = 9,635.73/87.80
  6. Step 6: Final answer
    x = 109.75

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.