Finding the Fourth Proportional to 1,399.54, 1,931.29 and 778.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.54 : 1,931.29 = 778.50 : x
2. Step 2: Convert to fraction form
   1,399.54/1,931.29 = 778.50/x
3. Step 3: Cross multiply
   1,399.54x = 1,931.29 × 778.50
4. Step 4: Simplify right side
   1,399.54x = 1,503,509.27
5. Step 5: Solve for x
   x = 1,503,509.27/1,399.54
6. Step 6: Final answer
   x = 1,074.29