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Finding the Fourth Proportional to 861.57, 1,294.55 and 811.78

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Solution

The fourth proportional to 861.57, 1,294.55 and 811.78 is: 1,219.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.57 : 1,294.55 = 811.78 : x
  2. Step 2: Convert to fraction form
    861.57/1,294.55 = 811.78/x
  3. Step 3: Cross multiply
    861.57x = 1,294.55 × 811.78
  4. Step 4: Simplify right side
    861.57x = 1,050,889.80
  5. Step 5: Solve for x
    x = 1,050,889.80/861.57
  6. Step 6: Final answer
    x = 1,219.74

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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.