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Finding the Fourth Proportional to 15.85, 21.85 and 12.40

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Solution

The fourth proportional to 15.85, 21.85 and 12.40 is: 17.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.85 : 21.85 = 12.40 : x
  2. Step 2: Convert to fraction form
    15.85/21.85 = 12.40/x
  3. Step 3: Cross multiply
    15.85x = 21.85 × 12.40
  4. Step 4: Simplify right side
    15.85x = 270.94
  5. Step 5: Solve for x
    x = 270.94/15.85
  6. Step 6: Final answer
    x = 17.09

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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.