Finding the Fourth Proportional to 2,639.31, 3,958.57 and 790.35

Step by Step Solution

1. Step 1: Write the proportion equation
   2,639.31 : 3,958.57 = 790.35 : x
2. Step 2: Convert to fraction form
   2,639.31/3,958.57 = 790.35/x
3. Step 3: Cross multiply
   2,639.31x = 3,958.57 × 790.35
4. Step 4: Simplify right side
   2,639.31x = 3,128,655.80
5. Step 5: Solve for x
   x = 3,128,655.80/2,639.31
6. Step 6: Final answer
   x = 1,185.41