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Finding the Fourth Proportional to 920.79, 1,379.74 and 642.87

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Solution

The fourth proportional to 920.79, 1,379.74 and 642.87 is: 963.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    920.79 : 1,379.74 = 642.87 : x
  2. Step 2: Convert to fraction form
    920.79/1,379.74 = 642.87/x
  3. Step 3: Cross multiply
    920.79x = 1,379.74 × 642.87
  4. Step 4: Simplify right side
    920.79x = 886,991.85
  5. Step 5: Solve for x
    x = 886,991.85/920.79
  6. Step 6: Final answer
    x = 963.29

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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.