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Finding the Fourth Proportional to 919.78, 1,269.30 and 505.78

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Solution

The fourth proportional to 919.78, 1,269.30 and 505.78 is: 697.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    919.78 : 1,269.30 = 505.78 : x
  2. Step 2: Convert to fraction form
    919.78/1,269.30 = 505.78/x
  3. Step 3: Cross multiply
    919.78x = 1,269.30 × 505.78
  4. Step 4: Simplify right side
    919.78x = 641,989.73
  5. Step 5: Solve for x
    x = 641,989.73/919.78
  6. Step 6: Final answer
    x = 697.98

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.