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Finding the Fourth Proportional to 15.89, 21.89 and 12.80

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Solution

The fourth proportional to 15.89, 21.89 and 12.80 is: 17.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.89 : 21.89 = 12.80 : x
  2. Step 2: Convert to fraction form
    15.89/21.89 = 12.80/x
  3. Step 3: Cross multiply
    15.89x = 21.89 × 12.80
  4. Step 4: Simplify right side
    15.89x = 280.02
  5. Step 5: Solve for x
    x = 280.02/15.89
  6. Step 6: Final answer
    x = 17.63

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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.