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Finding the Fourth Proportional to 87.72, 121.08 and 56.64

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Solution

The fourth proportional to 87.72, 121.08 and 56.64 is: 78.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.72 : 121.08 = 56.64 : x
  2. Step 2: Convert to fraction form
    87.72/121.08 = 56.64/x
  3. Step 3: Cross multiply
    87.72x = 121.08 × 56.64
  4. Step 4: Simplify right side
    87.72x = 6,857.97
  5. Step 5: Solve for x
    x = 6,857.97/87.72
  6. Step 6: Final answer
    x = 78.18

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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.