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Finding the Fourth Proportional to 639.05, 881.90 and 390.30

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Solution

The fourth proportional to 639.05, 881.90 and 390.30 is: 538.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.05 : 881.90 = 390.30 : x
  2. Step 2: Convert to fraction form
    639.05/881.90 = 390.30/x
  3. Step 3: Cross multiply
    639.05x = 881.90 × 390.30
  4. Step 4: Simplify right side
    639.05x = 344,203.62
  5. Step 5: Solve for x
    x = 344,203.62/639.05
  6. Step 6: Final answer
    x = 538.62

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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.