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Finding the Fourth Proportional to 87.68, 121.20 and 65.90

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Solution

The fourth proportional to 87.68, 121.20 and 65.90 is: 91.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.68 : 121.20 = 65.90 : x
  2. Step 2: Convert to fraction form
    87.68/121.20 = 65.90/x
  3. Step 3: Cross multiply
    87.68x = 121.20 × 65.90
  4. Step 4: Simplify right side
    87.68x = 7,987.08
  5. Step 5: Solve for x
    x = 7,987.08/87.68
  6. Step 6: Final answer
    x = 91.09

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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.