Finding the Fourth Proportional to 1,389.05, 1,916.95 and 799.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.05 : 1,916.95 = 799.78 : x
2. Step 2: Convert to fraction form
   1,389.05/1,916.95 = 799.78/x
3. Step 3: Cross multiply
   1,389.05x = 1,916.95 × 799.78
4. Step 4: Simplify right side
   1,389.05x = 1,533,138.27
5. Step 5: Solve for x
   x = 1,533,138.27/1,389.05
6. Step 6: Final answer
   x = 1,103.73