Finding the Fourth Proportional to 1,399.60, 1,931.16 and 839.92

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.60 : 1,931.16 = 839.92 : x
2. Step 2: Convert to fraction form
   1,399.60/1,931.16 = 839.92/x
3. Step 3: Cross multiply
   1,399.60x = 1,931.16 × 839.92
4. Step 4: Simplify right side
   1,399.60x = 1,622,019.91
5. Step 5: Solve for x
   x = 1,622,019.91/1,399.60
6. Step 6: Final answer
   x = 1,158.92