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Finding the Fourth Proportional to 861.90, 1,291.83 and 313.79

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Solution

The fourth proportional to 861.90, 1,291.83 and 313.79 is: 470.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.90 : 1,291.83 = 313.79 : x
  2. Step 2: Convert to fraction form
    861.90/1,291.83 = 313.79/x
  3. Step 3: Cross multiply
    861.90x = 1,291.83 × 313.79
  4. Step 4: Simplify right side
    861.90x = 405,363.34
  5. Step 5: Solve for x
    x = 405,363.34/861.90
  6. Step 6: Final answer
    x = 470.31

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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.