Finding the Fourth Proportional to 1,399.83, 1,931.43 and 840.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.83 : 1,931.43 = 840.21 : x
2. Step 2: Convert to fraction form
   1,399.83/1,931.43 = 840.21/x
3. Step 3: Cross multiply
   1,399.83x = 1,931.43 × 840.21
4. Step 4: Simplify right side
   1,399.83x = 1,622,806.80
5. Step 5: Solve for x
   x = 1,622,806.80/1,399.83
6. Step 6: Final answer
   x = 1,159.29