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Finding the Fourth Proportional to 809.76, 1,215.72 and 399.24

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Solution

The fourth proportional to 809.76, 1,215.72 and 399.24 is: 599.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    809.76 : 1,215.72 = 399.24 : x
  2. Step 2: Convert to fraction form
    809.76/1,215.72 = 399.24/x
  3. Step 3: Cross multiply
    809.76x = 1,215.72 × 399.24
  4. Step 4: Simplify right side
    809.76x = 485,364.05
  5. Step 5: Solve for x
    x = 485,364.05/809.76
  6. Step 6: Final answer
    x = 599.39

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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.