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Finding the Fourth Proportional to 810.21, 1,215.60 and 399.30

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Solution

The fourth proportional to 810.21, 1,215.60 and 399.30 is: 599.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    810.21 : 1,215.60 = 399.30 : x
  2. Step 2: Convert to fraction form
    810.21/1,215.60 = 399.30/x
  3. Step 3: Cross multiply
    810.21x = 1,215.60 × 399.30
  4. Step 4: Simplify right side
    810.21x = 485,389.08
  5. Step 5: Solve for x
    x = 485,389.08/810.21
  6. Step 6: Final answer
    x = 599.09

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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.