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Finding the Fourth Proportional to 811.30, 1,215.60 and 399.55

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Solution

The fourth proportional to 811.30, 1,215.60 and 399.55 is: 598.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.30 : 1,215.60 = 399.55 : x
  2. Step 2: Convert to fraction form
    811.30/1,215.60 = 399.55/x
  3. Step 3: Cross multiply
    811.30x = 1,215.60 × 399.55
  4. Step 4: Simplify right side
    811.30x = 485,692.98
  5. Step 5: Solve for x
    x = 485,692.98/811.30
  6. Step 6: Final answer
    x = 598.66

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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.