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Finding the Fourth Proportional to 15.31, 21.12 and 9.85

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Solution

The fourth proportional to 15.31, 21.12 and 9.85 is: 13.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.31 : 21.12 = 9.85 : x
  2. Step 2: Convert to fraction form
    15.31/21.12 = 9.85/x
  3. Step 3: Cross multiply
    15.31x = 21.12 × 9.85
  4. Step 4: Simplify right side
    15.31x = 207.98
  5. Step 5: Solve for x
    x = 207.98/15.31
  6. Step 6: Final answer
    x = 13.59

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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.