Finding the Fourth Proportional to 2,638.86, 3,958.20 and 691.05

Step by Step Solution

1. Step 1: Write the proportion equation
   2,638.86 : 3,958.20 = 691.05 : x
2. Step 2: Convert to fraction form
   2,638.86/3,958.20 = 691.05/x
3. Step 3: Cross multiply
   2,638.86x = 3,958.20 × 691.05
4. Step 4: Simplify right side
   2,638.86x = 2,735,314.11
5. Step 5: Solve for x
   x = 2,735,314.11/2,638.86
6. Step 6: Final answer
   x = 1,036.55