Finding the Fourth Proportional to 1,380.81, 1,905.39 and 791.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.81 : 1,905.39 = 791.31 : x
2. Step 2: Convert to fraction form
   1,380.81/1,905.39 = 791.31/x
3. Step 3: Cross multiply
   1,380.81x = 1,905.39 × 791.31
4. Step 4: Simplify right side
   1,380.81x = 1,507,754.16
5. Step 5: Solve for x
   x = 1,507,754.16/1,380.81
6. Step 6: Final answer
   x = 1,091.93