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Finding the Fourth Proportional to 390.40, 585.20 and 216.80

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Solution

The fourth proportional to 390.40, 585.20 and 216.80 is: 324.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.40 : 585.20 = 216.80 : x
  2. Step 2: Convert to fraction form
    390.40/585.20 = 216.80/x
  3. Step 3: Cross multiply
    390.40x = 585.20 × 216.80
  4. Step 4: Simplify right side
    390.40x = 126,871.36
  5. Step 5: Solve for x
    x = 126,871.36/390.40
  6. Step 6: Final answer
    x = 324.98

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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.