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Finding the Fourth Proportional to 21.90, 30.12 and 21.78

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Solution

The fourth proportional to 21.90, 30.12 and 21.78 is: 29.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.90 : 30.12 = 21.78 : x
  2. Step 2: Convert to fraction form
    21.90/30.12 = 21.78/x
  3. Step 3: Cross multiply
    21.90x = 30.12 × 21.78
  4. Step 4: Simplify right side
    21.90x = 656.01
  5. Step 5: Solve for x
    x = 656.01/21.90
  6. Step 6: Final answer
    x = 29.95

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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.