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Finding the Fourth Proportional to 87, 129.80 and 78.88

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Solution

The fourth proportional to 87, 129.80 and 78.88 is: 117.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    87 : 129.80 = 78.88 : x
  2. Step 2: Convert to fraction form
    87/129.80 = 78.88/x
  3. Step 3: Cross multiply
    87x = 129.80 × 78.88
  4. Step 4: Simplify right side
    87x = 10,238.62
  5. Step 5: Solve for x
    x = 10,238.62/87
  6. Step 6: Final answer
    x = 117.69

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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.