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Finding the Fourth Proportional to 21.28, 31.72 and 20.92

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Solution

The fourth proportional to 21.28, 31.72 and 20.92 is: 31.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.28 : 31.72 = 20.92 : x
  2. Step 2: Convert to fraction form
    21.28/31.72 = 20.92/x
  3. Step 3: Cross multiply
    21.28x = 31.72 × 20.92
  4. Step 4: Simplify right side
    21.28x = 663.58
  5. Step 5: Solve for x
    x = 663.58/21.28
  6. Step 6: Final answer
    x = 31.18

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.