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Finding the Fourth Proportional to 640.80, 876.72 and 638.88

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Solution

The fourth proportional to 640.80, 876.72 and 638.88 is: 874.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    640.80 : 876.72 = 638.88 : x
  2. Step 2: Convert to fraction form
    640.80/876.72 = 638.88/x
  3. Step 3: Cross multiply
    640.80x = 876.72 × 638.88
  4. Step 4: Simplify right side
    640.80x = 560,118.87
  5. Step 5: Solve for x
    x = 560,118.87/640.80
  6. Step 6: Final answer
    x = 874.09

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.