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Finding the Fourth Proportional to 31.08, 42.84 and 21.85

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Solution

The fourth proportional to 31.08, 42.84 and 21.85 is: 30.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.08 : 42.84 = 21.85 : x
  2. Step 2: Convert to fraction form
    31.08/42.84 = 21.85/x
  3. Step 3: Cross multiply
    31.08x = 42.84 × 21.85
  4. Step 4: Simplify right side
    31.08x = 936.05
  5. Step 5: Solve for x
    x = 936.05/31.08
  6. Step 6: Final answer
    x = 30.12

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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.