Finding the Fourth Proportional to 1,428.56, 1,971.39 and 831.08

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.56 : 1,971.39 = 831.08 : x
2. Step 2: Convert to fraction form
   1,428.56/1,971.39 = 831.08/x
3. Step 3: Cross multiply
   1,428.56x = 1,971.39 × 831.08
4. Step 4: Simplify right side
   1,428.56x = 1,638,382.80
5. Step 5: Solve for x
   x = 1,638,382.80/1,428.56
6. Step 6: Final answer
   x = 1,146.88