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Finding the Fourth Proportional to 87.78, 121.20 and 56.70

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Solution

The fourth proportional to 87.78, 121.20 and 56.70 is: 78.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.78 : 121.20 = 56.70 : x
  2. Step 2: Convert to fraction form
    87.78/121.20 = 56.70/x
  3. Step 3: Cross multiply
    87.78x = 121.20 × 56.70
  4. Step 4: Simplify right side
    87.78x = 6,872.04
  5. Step 5: Solve for x
    x = 6,872.04/87.78
  6. Step 6: Final answer
    x = 78.29

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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.