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Finding the Fourth Proportional to 987.78, 1,363.62 and 638.70

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Solution

The fourth proportional to 987.78, 1,363.62 and 638.70 is: 881.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.78 : 1,363.62 = 638.70 : x
  2. Step 2: Convert to fraction form
    987.78/1,363.62 = 638.70/x
  3. Step 3: Cross multiply
    987.78x = 1,363.62 × 638.70
  4. Step 4: Simplify right side
    987.78x = 870,944.09
  5. Step 5: Solve for x
    x = 870,944.09/987.78
  6. Step 6: Final answer
    x = 881.72

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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.