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Finding the Fourth Proportional to 390.66, 585.42 and 217.20

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Solution

The fourth proportional to 390.66, 585.42 and 217.20 is: 325.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.66 : 585.42 = 217.20 : x
  2. Step 2: Convert to fraction form
    390.66/585.42 = 217.20/x
  3. Step 3: Cross multiply
    390.66x = 585.42 × 217.20
  4. Step 4: Simplify right side
    390.66x = 127,153.22
  5. Step 5: Solve for x
    x = 127,153.22/390.66
  6. Step 6: Final answer
    x = 325.48

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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.