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Finding the Fourth Proportional to 21.28, 31.69 and 20.36

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Solution

The fourth proportional to 21.28, 31.69 and 20.36 is: 30.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.28 : 31.69 = 20.36 : x
  2. Step 2: Convert to fraction form
    21.28/31.69 = 20.36/x
  3. Step 3: Cross multiply
    21.28x = 31.69 × 20.36
  4. Step 4: Simplify right side
    21.28x = 645.21
  5. Step 5: Solve for x
    x = 645.21/21.28
  6. Step 6: Final answer
    x = 30.32

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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.