Finding the Fourth Proportional to 2,636.15, 3,953.50 and 991.80

Step by Step Solution

1. Step 1: Write the proportion equation
   2,636.15 : 3,953.50 = 991.80 : x
2. Step 2: Convert to fraction form
   2,636.15/3,953.50 = 991.80/x
3. Step 3: Cross multiply
   2,636.15x = 3,953.50 × 991.80
4. Step 4: Simplify right side
   2,636.15x = 3,921,078.82
5. Step 5: Solve for x
   x = 3,921,078.82/2,636.15
6. Step 6: Final answer
   x = 1,487.43