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Finding the Fourth Proportional to 87.40, 121 and 85.76

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Solution

The fourth proportional to 87.40, 121 and 85.76 is: 118.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.40 : 121 = 85.76 : x
  2. Step 2: Convert to fraction form
    87.40/121 = 85.76/x
  3. Step 3: Cross multiply
    87.40x = 121 × 85.76
  4. Step 4: Simplify right side
    87.40x = 10,376.96
  5. Step 5: Solve for x
    x = 10,376.96/87.40
  6. Step 6: Final answer
    x = 118.73

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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.