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Finding the Fourth Proportional to 78.87, 118.31 and 21.09

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Solution

The fourth proportional to 78.87, 118.31 and 21.09 is: 31.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.87 : 118.31 = 21.09 : x
  2. Step 2: Convert to fraction form
    78.87/118.31 = 21.09/x
  3. Step 3: Cross multiply
    78.87x = 118.31 × 21.09
  4. Step 4: Simplify right side
    78.87x = 2,494.97
  5. Step 5: Solve for x
    x = 2,494.97/78.87
  6. Step 6: Final answer
    x = 31.63

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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.