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Finding the Fourth Proportional to 691.61, 1,039.46 and 640.68

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Solution

The fourth proportional to 691.61, 1,039.46 and 640.68 is: 962.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    691.61 : 1,039.46 = 640.68 : x
  2. Step 2: Convert to fraction form
    691.61/1,039.46 = 640.68/x
  3. Step 3: Cross multiply
    691.61x = 1,039.46 × 640.68
  4. Step 4: Simplify right side
    691.61x = 665,961.23
  5. Step 5: Solve for x
    x = 665,961.23/691.61
  6. Step 6: Final answer
    x = 962.91

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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.