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Finding the Fourth Proportional to 21, 28.68 and 20.20

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Solution

The fourth proportional to 21, 28.68 and 20.20 is: 27.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    21 : 28.68 = 20.20 : x
  2. Step 2: Convert to fraction form
    21/28.68 = 20.20/x
  3. Step 3: Cross multiply
    21x = 28.68 × 20.20
  4. Step 4: Simplify right side
    21x = 579.34
  5. Step 5: Solve for x
    x = 579.34/21
  6. Step 6: Final answer
    x = 27.59

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.