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Finding the Fourth Proportional to 21.05, 31.74 and 20.75

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Solution

The fourth proportional to 21.05, 31.74 and 20.75 is: 31.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.05 : 31.74 = 20.75 : x
  2. Step 2: Convert to fraction form
    21.05/31.74 = 20.75/x
  3. Step 3: Cross multiply
    21.05x = 31.74 × 20.75
  4. Step 4: Simplify right side
    21.05x = 658.49
  5. Step 5: Solve for x
    x = 658.49/21.05
  6. Step 6: Final answer
    x = 31.28

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.