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Finding the Fourth Proportional to 30.91, 42.68 and 21.22

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Solution

The fourth proportional to 30.91, 42.68 and 21.22 is: 29.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.91 : 42.68 = 21.22 : x
  2. Step 2: Convert to fraction form
    30.91/42.68 = 21.22/x
  3. Step 3: Cross multiply
    30.91x = 42.68 × 21.22
  4. Step 4: Simplify right side
    30.91x = 905.67
  5. Step 5: Solve for x
    x = 905.67/30.91
  6. Step 6: Final answer
    x = 29.30

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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.