Finding the Fourth Proportional to 2,891.60, 4,338.12 and 811.61

Step by Step Solution

1. Step 1: Write the proportion equation
   2,891.60 : 4,338.12 = 811.61 : x
2. Step 2: Convert to fraction form
   2,891.60/4,338.12 = 811.61/x
3. Step 3: Cross multiply
   2,891.60x = 4,338.12 × 811.61
4. Step 4: Simplify right side
   2,891.60x = 3,520,839.88
5. Step 5: Solve for x
   x = 3,520,839.88/2,891.60
6. Step 6: Final answer
   x = 1,217.61