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Finding the Fourth Proportional to 87.91, 121.34 and 56.81

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Solution

The fourth proportional to 87.91, 121.34 and 56.81 is: 78.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.91 : 121.34 = 56.81 : x
  2. Step 2: Convert to fraction form
    87.91/121.34 = 56.81/x
  3. Step 3: Cross multiply
    87.91x = 121.34 × 56.81
  4. Step 4: Simplify right side
    87.91x = 6,893.33
  5. Step 5: Solve for x
    x = 6,893.33/87.91
  6. Step 6: Final answer
    x = 78.41

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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.