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Finding the Fourth Proportional to 78.90, 108.15 and 77.85

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Solution

The fourth proportional to 78.90, 108.15 and 77.85 is: 106.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.90 : 108.15 = 77.85 : x
  2. Step 2: Convert to fraction form
    78.90/108.15 = 77.85/x
  3. Step 3: Cross multiply
    78.90x = 108.15 × 77.85
  4. Step 4: Simplify right side
    78.90x = 8,419.48
  5. Step 5: Solve for x
    x = 8,419.48/78.90
  6. Step 6: Final answer
    x = 106.71

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.