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Finding the Fourth Proportional to 87.65, 121.08 and 65.78

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Solution

The fourth proportional to 87.65, 121.08 and 65.78 is: 90.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.65 : 121.08 = 65.78 : x
  2. Step 2: Convert to fraction form
    87.65/121.08 = 65.78/x
  3. Step 3: Cross multiply
    87.65x = 121.08 × 65.78
  4. Step 4: Simplify right side
    87.65x = 7,964.64
  5. Step 5: Solve for x
    x = 7,964.64/87.65
  6. Step 6: Final answer
    x = 90.87

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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.