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Finding the Fourth Proportional to 21.87, 32.81 and 20.72

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Solution

The fourth proportional to 21.87, 32.81 and 20.72 is: 31.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.87 : 32.81 = 20.72 : x
  2. Step 2: Convert to fraction form
    21.87/32.81 = 20.72/x
  3. Step 3: Cross multiply
    21.87x = 32.81 × 20.72
  4. Step 4: Simplify right side
    21.87x = 679.82
  5. Step 5: Solve for x
    x = 679.82/21.87
  6. Step 6: Final answer
    x = 31.08

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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.