Finding the Fourth Proportional to 1,040.40, 1,431.50 and 900.06

Step by Step Solution

1. Step 1: Write the proportion equation
   1,040.40 : 1,431.50 = 900.06 : x
2. Step 2: Convert to fraction form
   1,040.40/1,431.50 = 900.06/x
3. Step 3: Cross multiply
   1,040.40x = 1,431.50 × 900.06
4. Step 4: Simplify right side
   1,040.40x = 1,288,435.89
5. Step 5: Solve for x
   x = 1,288,435.89/1,040.40
6. Step 6: Final answer
   x = 1,238.40