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Finding the Fourth Proportional to 1,121.86, 1,682.81 and 428.85

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Solution

The fourth proportional to 1,121.86, 1,682.81 and 428.85 is: 643.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.86 : 1,682.81 = 428.85 : x
  2. Step 2: Convert to fraction form
    1,121.86/1,682.81 = 428.85/x
  3. Step 3: Cross multiply
    1,121.86x = 1,682.81 × 428.85
  4. Step 4: Simplify right side
    1,121.86x = 721,673.07
  5. Step 5: Solve for x
    x = 721,673.07/1,121.86
  6. Step 6: Final answer
    x = 643.28

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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.