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Finding the Fourth Proportional to 809.90, 1,215 and 398.93

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Solution

The fourth proportional to 809.90, 1,215 and 398.93 is: 598.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    809.90 : 1,215 = 398.93 : x
  2. Step 2: Convert to fraction form
    809.90/1,215 = 398.93/x
  3. Step 3: Cross multiply
    809.90x = 1,215 × 398.93
  4. Step 4: Simplify right side
    809.90x = 484,693.88
  5. Step 5: Solve for x
    x = 484,693.88/809.90
  6. Step 6: Final answer
    x = 598.46

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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.