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Finding the Fourth Proportional to 861.09, 1,291.63 and 428.14

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Solution

The fourth proportional to 861.09, 1,291.63 and 428.14 is: 642.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.09 : 1,291.63 = 428.14 : x
  2. Step 2: Convert to fraction form
    861.09/1,291.63 = 428.14/x
  3. Step 3: Cross multiply
    861.09x = 1,291.63 × 428.14
  4. Step 4: Simplify right side
    861.09x = 552,998.47
  5. Step 5: Solve for x
    x = 552,998.47/861.09
  6. Step 6: Final answer
    x = 642.21

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.