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Finding the Fourth Proportional to 1,321.78, 1,981.32 and 860.49

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Solution

The fourth proportional to 1,321.78, 1,981.32 and 860.49 is: 1,289.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,321.78 : 1,981.32 = 860.49 : x
  2. Step 2: Convert to fraction form
    1,321.78/1,981.32 = 860.49/x
  3. Step 3: Cross multiply
    1,321.78x = 1,981.32 × 860.49
  4. Step 4: Simplify right side
    1,321.78x = 1,704,906.05
  5. Step 5: Solve for x
    x = 1,704,906.05/1,321.78
  6. Step 6: Final answer
    x = 1,289.86

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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.