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Finding the Fourth Proportional to 78.69, 117.96 and 54.78

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Solution

The fourth proportional to 78.69, 117.96 and 54.78 is: 82.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.69 : 117.96 = 54.78 : x
  2. Step 2: Convert to fraction form
    78.69/117.96 = 54.78/x
  3. Step 3: Cross multiply
    78.69x = 117.96 × 54.78
  4. Step 4: Simplify right side
    78.69x = 6,461.85
  5. Step 5: Solve for x
    x = 6,461.85/78.69
  6. Step 6: Final answer
    x = 82.12

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.