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Finding the Fourth Proportional to 20.85, 28.76 and 13.56

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Solution

The fourth proportional to 20.85, 28.76 and 13.56 is: 18.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.85 : 28.76 = 13.56 : x
  2. Step 2: Convert to fraction form
    20.85/28.76 = 13.56/x
  3. Step 3: Cross multiply
    20.85x = 28.76 × 13.56
  4. Step 4: Simplify right side
    20.85x = 389.99
  5. Step 5: Solve for x
    x = 389.99/20.85
  6. Step 6: Final answer
    x = 18.70

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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.