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Finding the Fourth Proportional to 919.11, 1,378.67 and 431.90

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Solution

The fourth proportional to 919.11, 1,378.67 and 431.90 is: 647.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    919.11 : 1,378.67 = 431.90 : x
  2. Step 2: Convert to fraction form
    919.11/1,378.67 = 431.90/x
  3. Step 3: Cross multiply
    919.11x = 1,378.67 × 431.90
  4. Step 4: Simplify right side
    919.11x = 595,447.57
  5. Step 5: Solve for x
    x = 595,447.57/919.11
  6. Step 6: Final answer
    x = 647.85

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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.