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Finding the Fourth Proportional to 639.19, 881.85 and 390.42

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Solution

The fourth proportional to 639.19, 881.85 and 390.42 is: 538.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.19 : 881.85 = 390.42 : x
  2. Step 2: Convert to fraction form
    639.19/881.85 = 390.42/x
  3. Step 3: Cross multiply
    639.19x = 881.85 × 390.42
  4. Step 4: Simplify right side
    639.19x = 344,293.34
  5. Step 5: Solve for x
    x = 344,293.34/639.19
  6. Step 6: Final answer
    x = 538.64

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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.