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Finding the Fourth Proportional to 21.72, 30.18 and 21.42

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Solution

The fourth proportional to 21.72, 30.18 and 21.42 is: 29.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.72 : 30.18 = 21.42 : x
  2. Step 2: Convert to fraction form
    21.72/30.18 = 21.42/x
  3. Step 3: Cross multiply
    21.72x = 30.18 × 21.42
  4. Step 4: Simplify right side
    21.72x = 646.46
  5. Step 5: Solve for x
    x = 646.46/21.72
  6. Step 6: Final answer
    x = 29.76

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Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.