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Finding the Fourth Proportional to 861.72, 1,292.70 and 313.80

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Solution

The fourth proportional to 861.72, 1,292.70 and 313.80 is: 470.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.72 : 1,292.70 = 313.80 : x
  2. Step 2: Convert to fraction form
    861.72/1,292.70 = 313.80/x
  3. Step 3: Cross multiply
    861.72x = 1,292.70 × 313.80
  4. Step 4: Simplify right side
    861.72x = 405,649.26
  5. Step 5: Solve for x
    x = 405,649.26/861.72
  6. Step 6: Final answer
    x = 470.74

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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.