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Finding the Fourth Proportional to 65.75, 90.78 and 39.92

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Solution

The fourth proportional to 65.75, 90.78 and 39.92 is: 55.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    65.75 : 90.78 = 39.92 : x
  2. Step 2: Convert to fraction form
    65.75/90.78 = 39.92/x
  3. Step 3: Cross multiply
    65.75x = 90.78 × 39.92
  4. Step 4: Simplify right side
    65.75x = 3,623.94
  5. Step 5: Solve for x
    x = 3,623.94/65.75
  6. Step 6: Final answer
    x = 55.12

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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.