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Finding the Fourth Proportional to 861.80, 1,292.70 and 821.30

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Solution

The fourth proportional to 861.80, 1,292.70 and 821.30 is: 1,231.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.80 : 1,292.70 = 821.30 : x
  2. Step 2: Convert to fraction form
    861.80/1,292.70 = 821.30/x
  3. Step 3: Cross multiply
    861.80x = 1,292.70 × 821.30
  4. Step 4: Simplify right side
    861.80x = 1,061,694.51
  5. Step 5: Solve for x
    x = 1,061,694.51/861.80
  6. Step 6: Final answer
    x = 1,231.95

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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.