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Finding the Fourth Proportional to 638.79, 881.56 and 390.09

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Solution

The fourth proportional to 638.79, 881.56 and 390.09 is: 538.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    638.79 : 881.56 = 390.09 : x
  2. Step 2: Convert to fraction form
    638.79/881.56 = 390.09/x
  3. Step 3: Cross multiply
    638.79x = 881.56 × 390.09
  4. Step 4: Simplify right side
    638.79x = 343,887.96
  5. Step 5: Solve for x
    x = 343,887.96/638.79
  6. Step 6: Final answer
    x = 538.35

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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.