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Finding the Fourth Proportional to 20.86, 28.78 and 13.57

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Solution

The fourth proportional to 20.86, 28.78 and 13.57 is: 18.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.86 : 28.78 = 13.57 : x
  2. Step 2: Convert to fraction form
    20.86/28.78 = 13.57/x
  3. Step 3: Cross multiply
    20.86x = 28.78 × 13.57
  4. Step 4: Simplify right side
    20.86x = 390.44
  5. Step 5: Solve for x
    x = 390.44/20.86
  6. Step 6: Final answer
    x = 18.72

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.