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Finding the Fourth Proportional to 821.66, 1,231.20 and 561.78

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Solution

The fourth proportional to 821.66, 1,231.20 and 561.78 is: 841.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    821.66 : 1,231.20 = 561.78 : x
  2. Step 2: Convert to fraction form
    821.66/1,231.20 = 561.78/x
  3. Step 3: Cross multiply
    821.66x = 1,231.20 × 561.78
  4. Step 4: Simplify right side
    821.66x = 691,663.54
  5. Step 5: Solve for x
    x = 691,663.54/821.66
  6. Step 6: Final answer
    x = 841.79

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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.