Finding the Fourth Proportional to 2,478.38, 3,716.20 and 811.72

Step by Step Solution

1. Step 1: Write the proportion equation
   2,478.38 : 3,716.20 = 811.72 : x
2. Step 2: Convert to fraction form
   2,478.38/3,716.20 = 811.72/x
3. Step 3: Cross multiply
   2,478.38x = 3,716.20 × 811.72
4. Step 4: Simplify right side
   2,478.38x = 3,016,513.86
5. Step 5: Solve for x
   x = 3,016,513.86/2,478.38
6. Step 6: Final answer
   x = 1,217.13