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Finding the Fourth Proportional to 811.05, 1,215.23 and 399.30

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Solution

The fourth proportional to 811.05, 1,215.23 and 399.30 is: 598.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.05 : 1,215.23 = 399.30 : x
  2. Step 2: Convert to fraction form
    811.05/1,215.23 = 399.30/x
  3. Step 3: Cross multiply
    811.05x = 1,215.23 × 399.30
  4. Step 4: Simplify right side
    811.05x = 485,239.34
  5. Step 5: Solve for x
    x = 485,239.34/811.05
  6. Step 6: Final answer
    x = 598.29

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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.