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Finding the Fourth Proportional to 639.21, 881.84 and 390.47

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Solution

The fourth proportional to 639.21, 881.84 and 390.47 is: 538.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.21 : 881.84 = 390.47 : x
  2. Step 2: Convert to fraction form
    639.21/881.84 = 390.47/x
  3. Step 3: Cross multiply
    639.21x = 881.84 × 390.47
  4. Step 4: Simplify right side
    639.21x = 344,332.06
  5. Step 5: Solve for x
    x = 344,332.06/639.21
  6. Step 6: Final answer
    x = 538.68

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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.