Finding the Fourth Proportional to 1,398.81, 1,930.43 and 839.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.81 : 1,930.43 = 839.31 : x
2. Step 2: Convert to fraction form
   1,398.81/1,930.43 = 839.31/x
3. Step 3: Cross multiply
   1,398.81x = 1,930.43 × 839.31
4. Step 4: Simplify right side
   1,398.81x = 1,620,225.01
5. Step 5: Solve for x
   x = 1,620,225.01/1,398.81
6. Step 6: Final answer
   x = 1,158.29