Finding the Fourth Proportional to 1,039.21, 1,431.32 and 899.33

Step by Step Solution

1. Step 1: Write the proportion equation
   1,039.21 : 1,431.32 = 899.33 : x
2. Step 2: Convert to fraction form
   1,039.21/1,431.32 = 899.33/x
3. Step 3: Cross multiply
   1,039.21x = 1,431.32 × 899.33
4. Step 4: Simplify right side
   1,039.21x = 1,287,227.89
5. Step 5: Solve for x
   x = 1,287,227.89/1,039.21
6. Step 6: Final answer
   x = 1,238.66