Finding the Fourth Proportional to 1,387.78, 1,915.23 and 798.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.78 : 1,915.23 = 798.55 : x
2. Step 2: Convert to fraction form
   1,387.78/1,915.23 = 798.55/x
3. Step 3: Cross multiply
   1,387.78x = 1,915.23 × 798.55
4. Step 4: Simplify right side
   1,387.78x = 1,529,406.92
5. Step 5: Solve for x
   x = 1,529,406.92/1,387.78
6. Step 6: Final answer
   x = 1,102.05