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Finding the Fourth Proportional to 987.75, 1,363.50 and 638.64

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Solution

The fourth proportional to 987.75, 1,363.50 and 638.64 is: 881.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.75 : 1,363.50 = 638.64 : x
  2. Step 2: Convert to fraction form
    987.75/1,363.50 = 638.64/x
  3. Step 3: Cross multiply
    987.75x = 1,363.50 × 638.64
  4. Step 4: Simplify right side
    987.75x = 870,785.64
  5. Step 5: Solve for x
    x = 870,785.64/987.75
  6. Step 6: Final answer
    x = 881.59

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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.