Finding the Fourth Proportional to 1,399.05, 1,931.31 and 839.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.05 : 1,931.31 = 839.61 : x
2. Step 2: Convert to fraction form
   1,399.05/1,931.31 = 839.61/x
3. Step 3: Cross multiply
   1,399.05x = 1,931.31 × 839.61
4. Step 4: Simplify right side
   1,399.05x = 1,621,547.19
5. Step 5: Solve for x
   x = 1,621,547.19/1,399.05
6. Step 6: Final answer
   x = 1,159.03