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Finding the Fourth Proportional to 861.71, 1,187.19 and 640.31

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Solution

The fourth proportional to 861.71, 1,187.19 and 640.31 is: 882.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.71 : 1,187.19 = 640.31 : x
  2. Step 2: Convert to fraction form
    861.71/1,187.19 = 640.31/x
  3. Step 3: Cross multiply
    861.71x = 1,187.19 × 640.31
  4. Step 4: Simplify right side
    861.71x = 760,163.69
  5. Step 5: Solve for x
    x = 760,163.69/861.71
  6. Step 6: Final answer
    x = 882.16

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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.