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Finding the Fourth Proportional to 78.78, 118.20 and 66.90

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Solution

The fourth proportional to 78.78, 118.20 and 66.90 is: 100.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.78 : 118.20 = 66.90 : x
  2. Step 2: Convert to fraction form
    78.78/118.20 = 66.90/x
  3. Step 3: Cross multiply
    78.78x = 118.20 × 66.90
  4. Step 4: Simplify right side
    78.78x = 7,907.58
  5. Step 5: Solve for x
    x = 7,907.58/78.78
  6. Step 6: Final answer
    x = 100.38

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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.