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Finding the Fourth Proportional to 861.15, 1,291.42 and 398.84

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Solution

The fourth proportional to 861.15, 1,291.42 and 398.84 is: 598.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.15 : 1,291.42 = 398.84 : x
  2. Step 2: Convert to fraction form
    861.15/1,291.42 = 398.84/x
  3. Step 3: Cross multiply
    861.15x = 1,291.42 × 398.84
  4. Step 4: Simplify right side
    861.15x = 515,070.14
  5. Step 5: Solve for x
    x = 515,070.14/861.15
  6. Step 6: Final answer
    x = 598.12

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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.