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Finding the Fourth Proportional to 15.81, 21.92 and 15.15

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Solution

The fourth proportional to 15.81, 21.92 and 15.15 is: 21.00

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.81 : 21.92 = 15.15 : x
  2. Step 2: Convert to fraction form
    15.81/21.92 = 15.15/x
  3. Step 3: Cross multiply
    15.81x = 21.92 × 15.15
  4. Step 4: Simplify right side
    15.81x = 332.09
  5. Step 5: Solve for x
    x = 332.09/15.81
  6. Step 6: Final answer
    x = 21.00

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Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.