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Finding the Fourth Proportional to 987.74, 1,363.61 and 721.91

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Solution

The fourth proportional to 987.74, 1,363.61 and 721.91 is: 996.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.74 : 1,363.61 = 721.91 : x
  2. Step 2: Convert to fraction form
    987.74/1,363.61 = 721.91/x
  3. Step 3: Cross multiply
    987.74x = 1,363.61 × 721.91
  4. Step 4: Simplify right side
    987.74x = 984,398.68
  5. Step 5: Solve for x
    x = 984,398.68/987.74
  6. Step 6: Final answer
    x = 996.61

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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.