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Finding the Fourth Proportional to 987.81, 1,363.14 and 638.51

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Solution

The fourth proportional to 987.81, 1,363.14 and 638.51 is: 881.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.81 : 1,363.14 = 638.51 : x
  2. Step 2: Convert to fraction form
    987.81/1,363.14 = 638.51/x
  3. Step 3: Cross multiply
    987.81x = 1,363.14 × 638.51
  4. Step 4: Simplify right side
    987.81x = 870,371.71
  5. Step 5: Solve for x
    x = 870,371.71/987.81
  6. Step 6: Final answer
    x = 881.11

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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.