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Finding the Fourth Proportional to 87.15, 131.27 and 85.40

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Solution

The fourth proportional to 87.15, 131.27 and 85.40 is: 128.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.15 : 131.27 = 85.40 : x
  2. Step 2: Convert to fraction form
    87.15/131.27 = 85.40/x
  3. Step 3: Cross multiply
    87.15x = 131.27 × 85.40
  4. Step 4: Simplify right side
    87.15x = 11,210.02
  5. Step 5: Solve for x
    x = 11,210.02/87.15
  6. Step 6: Final answer
    x = 128.63

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.