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Finding the Fourth Proportional to 21.89, 30.21 and 13.70

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Solution

The fourth proportional to 21.89, 30.21 and 13.70 is: 18.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.89 : 30.21 = 13.70 : x
  2. Step 2: Convert to fraction form
    21.89/30.21 = 13.70/x
  3. Step 3: Cross multiply
    21.89x = 30.21 × 13.70
  4. Step 4: Simplify right side
    21.89x = 413.95
  5. Step 5: Solve for x
    x = 413.95/21.89
  6. Step 6: Final answer
    x = 18.91

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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.