Finding the Fourth Proportional to 1,386.40, 1,912.80 and 796.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.40 : 1,912.80 = 796.72 : x
2. Step 2: Convert to fraction form
   1,386.40/1,912.80 = 796.72/x
3. Step 3: Cross multiply
   1,386.40x = 1,912.80 × 796.72
4. Step 4: Simplify right side
   1,386.40x = 1,523,966.02
5. Step 5: Solve for x
   x = 1,523,966.02/1,386.40
6. Step 6: Final answer
   x = 1,099.23