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Finding the Fourth Proportional to 639.32, 881.79 and 390.43

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Solution

The fourth proportional to 639.32, 881.79 and 390.43 is: 538.51

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.32 : 881.79 = 390.43 : x
  2. Step 2: Convert to fraction form
    639.32/881.79 = 390.43/x
  3. Step 3: Cross multiply
    639.32x = 881.79 × 390.43
  4. Step 4: Simplify right side
    639.32x = 344,278.15
  5. Step 5: Solve for x
    x = 344,278.15/639.32
  6. Step 6: Final answer
    x = 538.51

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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.