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Finding the Fourth Proportional to 820.90, 1,231.21 and 409.60

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Solution

The fourth proportional to 820.90, 1,231.21 and 409.60 is: 614.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    820.90 : 1,231.21 = 409.60 : x
  2. Step 2: Convert to fraction form
    820.90/1,231.21 = 409.60/x
  3. Step 3: Cross multiply
    820.90x = 1,231.21 × 409.60
  4. Step 4: Simplify right side
    820.90x = 504,303.62
  5. Step 5: Solve for x
    x = 504,303.62/820.90
  6. Step 6: Final answer
    x = 614.33

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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.