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Finding the Fourth Proportional to 31.23, 43.09 and 21.90

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Solution

The fourth proportional to 31.23, 43.09 and 21.90 is: 30.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.23 : 43.09 = 21.90 : x
  2. Step 2: Convert to fraction form
    31.23/43.09 = 21.90/x
  3. Step 3: Cross multiply
    31.23x = 43.09 × 21.90
  4. Step 4: Simplify right side
    31.23x = 943.67
  5. Step 5: Solve for x
    x = 943.67/31.23
  6. Step 6: Final answer
    x = 30.22

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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.