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Finding the Fourth Proportional to 18.91, 28.38 and 8.78

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Solution

The fourth proportional to 18.91, 28.38 and 8.78 is: 13.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    18.91 : 28.38 = 8.78 : x
  2. Step 2: Convert to fraction form
    18.91/28.38 = 8.78/x
  3. Step 3: Cross multiply
    18.91x = 28.38 × 8.78
  4. Step 4: Simplify right side
    18.91x = 249.18
  5. Step 5: Solve for x
    x = 249.18/18.91
  6. Step 6: Final answer
    x = 13.18

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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.