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Finding the Fourth Proportional to 808.40, 1,213.20 and 321.80

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Solution

The fourth proportional to 808.40, 1,213.20 and 321.80 is: 482.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    808.40 : 1,213.20 = 321.80 : x
  2. Step 2: Convert to fraction form
    808.40/1,213.20 = 321.80/x
  3. Step 3: Cross multiply
    808.40x = 1,213.20 × 321.80
  4. Step 4: Simplify right side
    808.40x = 390,407.76
  5. Step 5: Solve for x
    x = 390,407.76/808.40
  6. Step 6: Final answer
    x = 482.94

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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.