Finding the Fourth Proportional to 2,665.64, 3,998.63 and 816.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,665.64 : 3,998.63 = 816.78 : x
2. Step 2: Convert to fraction form
   2,665.64/3,998.63 = 816.78/x
3. Step 3: Cross multiply
   2,665.64x = 3,998.63 × 816.78
4. Step 4: Simplify right side
   2,665.64x = 3,266,018.05
5. Step 5: Solve for x
   x = 3,266,018.05/2,665.64
6. Step 6: Final answer
   x = 1,225.23