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Finding the Fourth Proportional to 21.21, 28.90 and 20.74

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Solution

The fourth proportional to 21.21, 28.90 and 20.74 is: 28.26

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.21 : 28.90 = 20.74 : x
  2. Step 2: Convert to fraction form
    21.21/28.90 = 20.74/x
  3. Step 3: Cross multiply
    21.21x = 28.90 × 20.74
  4. Step 4: Simplify right side
    21.21x = 599.32
  5. Step 5: Solve for x
    x = 599.32/21.21
  6. Step 6: Final answer
    x = 28.26

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Why These Related Problems?

These problems maintain the same ratio (1.36) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.