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Finding the Fourth Proportional to 87.45, 120.78 and 65.71

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Solution

The fourth proportional to 87.45, 120.78 and 65.71 is: 90.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    87.45 : 120.78 = 65.71 : x
  2. Step 2: Convert to fraction form
    87.45/120.78 = 65.71/x
  3. Step 3: Cross multiply
    87.45x = 120.78 × 65.71
  4. Step 4: Simplify right side
    87.45x = 7,936.45
  5. Step 5: Solve for x
    x = 7,936.45/87.45
  6. Step 6: Final answer
    x = 90.75

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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.