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Finding the Fourth Proportional to 1,920.10, 2,880.78 and 687.70

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Solution

The fourth proportional to 1,920.10, 2,880.78 and 687.70 is: 1,031.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,920.10 : 2,880.78 = 687.70 : x
  2. Step 2: Convert to fraction form
    1,920.10/2,880.78 = 687.70/x
  3. Step 3: Cross multiply
    1,920.10x = 2,880.78 × 687.70
  4. Step 4: Simplify right side
    1,920.10x = 1,981,112.41
  5. Step 5: Solve for x
    x = 1,981,112.41/1,920.10
  6. Step 6: Final answer
    x = 1,031.78

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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.