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Finding the Fourth Proportional to 1,318.74, 1,978.11 and 769.78

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Solution

The fourth proportional to 1,318.74, 1,978.11 and 769.78 is: 1,154.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,318.74 : 1,978.11 = 769.78 : x
  2. Step 2: Convert to fraction form
    1,318.74/1,978.11 = 769.78/x
  3. Step 3: Cross multiply
    1,318.74x = 1,978.11 × 769.78
  4. Step 4: Simplify right side
    1,318.74x = 1,522,709.52
  5. Step 5: Solve for x
    x = 1,522,709.52/1,318.74
  6. Step 6: Final answer
    x = 1,154.67

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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.