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Finding the Fourth Proportional to 15.89, 21.86 and 15.78

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Solution

The fourth proportional to 15.89, 21.86 and 15.78 is: 21.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.89 : 21.86 = 15.78 : x
  2. Step 2: Convert to fraction form
    15.89/21.86 = 15.78/x
  3. Step 3: Cross multiply
    15.89x = 21.86 × 15.78
  4. Step 4: Simplify right side
    15.89x = 344.87
  5. Step 5: Solve for x
    x = 344.87/15.89
  6. Step 6: Final answer
    x = 21.71

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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.