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Finding the Fourth Proportional to 76.86, 105.82 and 65.78

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Solution

The fourth proportional to 76.86, 105.82 and 65.78 is: 90.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.86 : 105.82 = 65.78 : x
  2. Step 2: Convert to fraction form
    76.86/105.82 = 65.78/x
  3. Step 3: Cross multiply
    76.86x = 105.82 × 65.78
  4. Step 4: Simplify right side
    76.86x = 6,960.84
  5. Step 5: Solve for x
    x = 6,960.84/76.86
  6. Step 6: Final answer
    x = 90.57

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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.