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Finding the Fourth Proportional to 812.80, 1,219.20 and 620.80

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Solution

The fourth proportional to 812.80, 1,219.20 and 620.80 is: 931.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    812.80 : 1,219.20 = 620.80 : x
  2. Step 2: Convert to fraction form
    812.80/1,219.20 = 620.80/x
  3. Step 3: Cross multiply
    812.80x = 1,219.20 × 620.80
  4. Step 4: Simplify right side
    812.80x = 756,879.36
  5. Step 5: Solve for x
    x = 756,879.36/812.80
  6. Step 6: Final answer
    x = 931.20

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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.