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Finding the Fourth Proportional to 20.72, 31.05 and 15.65

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Solution

The fourth proportional to 20.72, 31.05 and 15.65 is: 23.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.72 : 31.05 = 15.65 : x
  2. Step 2: Convert to fraction form
    20.72/31.05 = 15.65/x
  3. Step 3: Cross multiply
    20.72x = 31.05 × 15.65
  4. Step 4: Simplify right side
    20.72x = 485.93
  5. Step 5: Solve for x
    x = 485.93/20.72
  6. Step 6: Final answer
    x = 23.45

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.