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Finding the Fourth Proportional to 390.78, 586.31 and 217.65

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Solution

The fourth proportional to 390.78, 586.31 and 217.65 is: 326.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.78 : 586.31 = 217.65 : x
  2. Step 2: Convert to fraction form
    390.78/586.31 = 217.65/x
  3. Step 3: Cross multiply
    390.78x = 586.31 × 217.65
  4. Step 4: Simplify right side
    390.78x = 127,610.37
  5. Step 5: Solve for x
    x = 127,610.37/390.78
  6. Step 6: Final answer
    x = 326.55

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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.