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Finding the Fourth Proportional to 28.40, 42.60 and 20.81

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Solution

The fourth proportional to 28.40, 42.60 and 20.81 is: 31.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    28.40 : 42.60 = 20.81 : x
  2. Step 2: Convert to fraction form
    28.40/42.60 = 20.81/x
  3. Step 3: Cross multiply
    28.40x = 42.60 × 20.81
  4. Step 4: Simplify right side
    28.40x = 886.39
  5. Step 5: Solve for x
    x = 886.39/28.40
  6. Step 6: Final answer
    x = 31.21

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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.