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Finding the Fourth Proportional to 691.43, 1,039.42 and 640.70

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Solution

The fourth proportional to 691.43, 1,039.42 and 640.70 is: 963.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    691.43 : 1,039.42 = 640.70 : x
  2. Step 2: Convert to fraction form
    691.43/1,039.42 = 640.70/x
  3. Step 3: Cross multiply
    691.43x = 1,039.42 × 640.70
  4. Step 4: Simplify right side
    691.43x = 665,958.99
  5. Step 5: Solve for x
    x = 665,958.99/691.43
  6. Step 6: Final answer
    x = 963.17

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.