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Finding the Fourth Proportional to 639.40, 882.18 and 390.66

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Solution

The fourth proportional to 639.40, 882.18 and 390.66 is: 538.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.40 : 882.18 = 390.66 : x
  2. Step 2: Convert to fraction form
    639.40/882.18 = 390.66/x
  3. Step 3: Cross multiply
    639.40x = 882.18 × 390.66
  4. Step 4: Simplify right side
    639.40x = 344,632.44
  5. Step 5: Solve for x
    x = 344,632.44/639.40
  6. Step 6: Final answer
    x = 538.99

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.