Finding the Fourth Proportional to 3,131.31, 4,697.43 and 939.78

Step by Step Solution

1. Step 1: Write the proportion equation
   3,131.31 : 4,697.43 = 939.78 : x
2. Step 2: Convert to fraction form
   3,131.31/4,697.43 = 939.78/x
3. Step 3: Cross multiply
   3,131.31x = 4,697.43 × 939.78
4. Step 4: Simplify right side
   3,131.31x = 4,414,550.77
5. Step 5: Solve for x
   x = 4,414,550.77/3,131.31
6. Step 6: Final answer
   x = 1,409.81