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Finding the Fourth Proportional to 638.94, 881.78 and 390.20

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Solution

The fourth proportional to 638.94, 881.78 and 390.20 is: 538.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    638.94 : 881.78 = 390.20 : x
  2. Step 2: Convert to fraction form
    638.94/881.78 = 390.20/x
  3. Step 3: Cross multiply
    638.94x = 881.78 × 390.20
  4. Step 4: Simplify right side
    638.94x = 344,064.20
  5. Step 5: Solve for x
    x = 344,064.20/638.94
  6. Step 6: Final answer
    x = 538.49

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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.