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Finding the Fourth Proportional to 20.64, 28.47 and 13.72

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Solution

The fourth proportional to 20.64, 28.47 and 13.72 is: 18.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.64 : 28.47 = 13.72 : x
  2. Step 2: Convert to fraction form
    20.64/28.47 = 13.72/x
  3. Step 3: Cross multiply
    20.64x = 28.47 × 13.72
  4. Step 4: Simplify right side
    20.64x = 390.61
  5. Step 5: Solve for x
    x = 390.61/20.64
  6. Step 6: Final answer
    x = 18.92

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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.