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Finding the Fourth Proportional to 20.65, 31 and 13.42

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Solution

The fourth proportional to 20.65, 31 and 13.42 is: 20.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.65 : 31 = 13.42 : x
  2. Step 2: Convert to fraction form
    20.65/31 = 13.42/x
  3. Step 3: Cross multiply
    20.65x = 31 × 13.42
  4. Step 4: Simplify right side
    20.65x = 416.02
  5. Step 5: Solve for x
    x = 416.02/20.65
  6. Step 6: Final answer
    x = 20.15

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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.