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Finding the Fourth Proportional to 30.81, 42.49 and 21.47

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Solution

The fourth proportional to 30.81, 42.49 and 21.47 is: 29.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.81 : 42.49 = 21.47 : x
  2. Step 2: Convert to fraction form
    30.81/42.49 = 21.47/x
  3. Step 3: Cross multiply
    30.81x = 42.49 × 21.47
  4. Step 4: Simplify right side
    30.81x = 912.15
  5. Step 5: Solve for x
    x = 912.15/30.81
  6. Step 6: Final answer
    x = 29.61

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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.