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Finding the Fourth Proportional to 20.95, 31.40 and 12.39

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Solution

The fourth proportional to 20.95, 31.40 and 12.39 is: 18.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.95 : 31.40 = 12.39 : x
  2. Step 2: Convert to fraction form
    20.95/31.40 = 12.39/x
  3. Step 3: Cross multiply
    20.95x = 31.40 × 12.39
  4. Step 4: Simplify right side
    20.95x = 388.98
  5. Step 5: Solve for x
    x = 388.98/20.95
  6. Step 6: Final answer
    x = 18.57

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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.