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Finding the Fourth Proportional to 21.72, 29.88 and 20.40

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Solution

The fourth proportional to 21.72, 29.88 and 20.40 is: 28.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.72 : 29.88 = 20.40 : x
  2. Step 2: Convert to fraction form
    21.72/29.88 = 20.40/x
  3. Step 3: Cross multiply
    21.72x = 29.88 × 20.40
  4. Step 4: Simplify right side
    21.72x = 609.55
  5. Step 5: Solve for x
    x = 609.55/21.72
  6. Step 6: Final answer
    x = 28.06

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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.