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Finding the Fourth Proportional to 321.78, 482.31 and 138.90

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Solution

The fourth proportional to 321.78, 482.31 and 138.90 is: 208.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    321.78 : 482.31 = 138.90 : x
  2. Step 2: Convert to fraction form
    321.78/482.31 = 138.90/x
  3. Step 3: Cross multiply
    321.78x = 482.31 × 138.90
  4. Step 4: Simplify right side
    321.78x = 66,992.86
  5. Step 5: Solve for x
    x = 66,992.86/321.78
  6. Step 6: Final answer
    x = 208.19

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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.