Finding the Fourth Proportional to 1,399.72, 1,931.70 and 778.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.72 : 1,931.70 = 778.72 : x
2. Step 2: Convert to fraction form
   1,399.72/1,931.70 = 778.72/x
3. Step 3: Cross multiply
   1,399.72x = 1,931.70 × 778.72
4. Step 4: Simplify right side
   1,399.72x = 1,504,253.42
5. Step 5: Solve for x
   x = 1,504,253.42/1,399.72
6. Step 6: Final answer
   x = 1,074.68