Finding the Fourth Proportional to 1,399.45, 1,931.40 and 840.10

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.45 : 1,931.40 = 840.10 : x
2. Step 2: Convert to fraction form
   1,399.45/1,931.40 = 840.10/x
3. Step 3: Cross multiply
   1,399.45x = 1,931.40 × 840.10
4. Step 4: Simplify right side
   1,399.45x = 1,622,569.14
5. Step 5: Solve for x
   x = 1,622,569.14/1,399.45
6. Step 6: Final answer
   x = 1,159.43