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Finding the Fourth Proportional to 811.62, 1,215.41 and 399.43

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Solution

The fourth proportional to 811.62, 1,215.41 and 399.43 is: 598.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.62 : 1,215.41 = 399.43 : x
  2. Step 2: Convert to fraction form
    811.62/1,215.41 = 399.43/x
  3. Step 3: Cross multiply
    811.62x = 1,215.41 × 399.43
  4. Step 4: Simplify right side
    811.62x = 485,470.74
  5. Step 5: Solve for x
    x = 485,470.74/811.62
  6. Step 6: Final answer
    x = 598.15

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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.