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Finding the Fourth Proportional to 87.90, 121.36 and 61.82

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Solution

The fourth proportional to 87.90, 121.36 and 61.82 is: 85.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.90 : 121.36 = 61.82 : x
  2. Step 2: Convert to fraction form
    87.90/121.36 = 61.82/x
  3. Step 3: Cross multiply
    87.90x = 121.36 × 61.82
  4. Step 4: Simplify right side
    87.90x = 7,502.48
  5. Step 5: Solve for x
    x = 7,502.48/87.90
  6. Step 6: Final answer
    x = 85.35

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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.