Finding the Fourth Proportional to 1,399.82, 1,931.42 and 840.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.82 : 1,931.42 = 840.20 : x
2. Step 2: Convert to fraction form
   1,399.82/1,931.42 = 840.20/x
3. Step 3: Cross multiply
   1,399.82x = 1,931.42 × 840.20
4. Step 4: Simplify right side
   1,399.82x = 1,622,779.08
5. Step 5: Solve for x
   x = 1,622,779.08/1,399.82
6. Step 6: Final answer
   x = 1,159.28