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Finding the Fourth Proportional to 31.09, 42.90 and 18.81

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Solution

The fourth proportional to 31.09, 42.90 and 18.81 is: 25.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.09 : 42.90 = 18.81 : x
  2. Step 2: Convert to fraction form
    31.09/42.90 = 18.81/x
  3. Step 3: Cross multiply
    31.09x = 42.90 × 18.81
  4. Step 4: Simplify right side
    31.09x = 806.95
  5. Step 5: Solve for x
    x = 806.95/31.09
  6. Step 6: Final answer
    x = 25.96

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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.