Finding the Fourth Proportional to 1,391.13, 1,919.78 and 801.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.13 : 1,919.78 = 801.57 : x
2. Step 2: Convert to fraction form
   1,391.13/1,919.78 = 801.57/x
3. Step 3: Cross multiply
   1,391.13x = 1,919.78 × 801.57
4. Step 4: Simplify right side
   1,391.13x = 1,538,838.05
5. Step 5: Solve for x
   x = 1,538,838.05/1,391.13
6. Step 6: Final answer
   x = 1,106.18