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Finding the Fourth Proportional to 1,317.85, 1,978.11 and 660.20

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Solution

The fourth proportional to 1,317.85, 1,978.11 and 660.20 is: 990.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,317.85 : 1,978.11 = 660.20 : x
  2. Step 2: Convert to fraction form
    1,317.85/1,978.11 = 660.20/x
  3. Step 3: Cross multiply
    1,317.85x = 1,978.11 × 660.20
  4. Step 4: Simplify right side
    1,317.85x = 1,305,949.87
  5. Step 5: Solve for x
    x = 1,305,949.87/1,317.85
  6. Step 6: Final answer
    x = 990.97

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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.