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Finding the Fourth Proportional to 21.05, 31.53 and 20.57

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Solution

The fourth proportional to 21.05, 31.53 and 20.57 is: 30.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.05 : 31.53 = 20.57 : x
  2. Step 2: Convert to fraction form
    21.05/31.53 = 20.57/x
  3. Step 3: Cross multiply
    21.05x = 31.53 × 20.57
  4. Step 4: Simplify right side
    21.05x = 648.65
  5. Step 5: Solve for x
    x = 648.65/21.05
  6. Step 6: Final answer
    x = 30.82

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.