Finding the Fourth Proportional to 1,399.50, 1,931.31 and 778.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.50 : 1,931.31 = 778.50 : x
2. Step 2: Convert to fraction form
   1,399.50/1,931.31 = 778.50/x
3. Step 3: Cross multiply
   1,399.50x = 1,931.31 × 778.50
4. Step 4: Simplify right side
   1,399.50x = 1,503,524.84
5. Step 5: Solve for x
   x = 1,503,524.84/1,399.50
6. Step 6: Final answer
   x = 1,074.33