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Finding the Fourth Proportional to 76.78, 105.84 and 54.91

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Solution

The fourth proportional to 76.78, 105.84 and 54.91 is: 75.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    76.78 : 105.84 = 54.91 : x
  2. Step 2: Convert to fraction form
    76.78/105.84 = 54.91/x
  3. Step 3: Cross multiply
    76.78x = 105.84 × 54.91
  4. Step 4: Simplify right side
    76.78x = 5,811.41
  5. Step 5: Solve for x
    x = 5,811.41/76.78
  6. Step 6: Final answer
    x = 75.69

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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.