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Finding the Fourth Proportional to 21.57, 29.78 and 15.11

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Solution

The fourth proportional to 21.57, 29.78 and 15.11 is: 20.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.57 : 29.78 = 15.11 : x
  2. Step 2: Convert to fraction form
    21.57/29.78 = 15.11/x
  3. Step 3: Cross multiply
    21.57x = 29.78 × 15.11
  4. Step 4: Simplify right side
    21.57x = 449.75
  5. Step 5: Solve for x
    x = 449.75/21.57
  6. Step 6: Final answer
    x = 20.85

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.