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Finding the Fourth Proportional to 861.39, 1,291.68 and 313.20

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Solution

The fourth proportional to 861.39, 1,291.68 and 313.20 is: 469.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.39 : 1,291.68 = 313.20 : x
  2. Step 2: Convert to fraction form
    861.39/1,291.68 = 313.20/x
  3. Step 3: Cross multiply
    861.39x = 1,291.68 × 313.20
  4. Step 4: Simplify right side
    861.39x = 404,554.18
  5. Step 5: Solve for x
    x = 404,554.18/861.39
  6. Step 6: Final answer
    x = 469.65

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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.