Finding the Fourth Proportional to 1,311.28, 1,968.72 and 822.88

Step by Step Solution

1. Step 1: Write the proportion equation
   1,311.28 : 1,968.72 = 822.88 : x
2. Step 2: Convert to fraction form
   1,311.28/1,968.72 = 822.88/x
3. Step 3: Cross multiply
   1,311.28x = 1,968.72 × 822.88
4. Step 4: Simplify right side
   1,311.28x = 1,620,020.31
5. Step 5: Solve for x
   x = 1,620,020.31/1,311.28
6. Step 6: Final answer
   x = 1,235.45