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Finding the Fourth Proportional to 87.15, 130.17 and 78.90

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Solution

The fourth proportional to 87.15, 130.17 and 78.90 is: 117.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.15 : 130.17 = 78.90 : x
  2. Step 2: Convert to fraction form
    87.15/130.17 = 78.90/x
  3. Step 3: Cross multiply
    87.15x = 130.17 × 78.90
  4. Step 4: Simplify right side
    87.15x = 10,270.51
  5. Step 5: Solve for x
    x = 10,270.51/87.15
  6. Step 6: Final answer
    x = 117.85

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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.