Finding the Fourth Proportional to 1,388.20, 1,915.12 and 798.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.20 : 1,915.12 = 798.61 : x
2. Step 2: Convert to fraction form
   1,388.20/1,915.12 = 798.61/x
3. Step 3: Cross multiply
   1,388.20x = 1,915.12 × 798.61
4. Step 4: Simplify right side
   1,388.20x = 1,529,433.98
5. Step 5: Solve for x
   x = 1,529,433.98/1,388.20
6. Step 6: Final answer
   x = 1,101.74