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Finding the Fourth Proportional to 1,120.72, 1,680.78 and 389.92

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Solution

The fourth proportional to 1,120.72, 1,680.78 and 389.92 is: 584.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.72 : 1,680.78 = 389.92 : x
  2. Step 2: Convert to fraction form
    1,120.72/1,680.78 = 389.92/x
  3. Step 3: Cross multiply
    1,120.72x = 1,680.78 × 389.92
  4. Step 4: Simplify right side
    1,120.72x = 655,369.74
  5. Step 5: Solve for x
    x = 655,369.74/1,120.72
  6. Step 6: Final answer
    x = 584.78

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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.