Finding the Fourth Proportional to 1,386.28, 1,912.57 and 818.99

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.28 : 1,912.57 = 818.99 : x
2. Step 2: Convert to fraction form
   1,386.28/1,912.57 = 818.99/x
3. Step 3: Cross multiply
   1,386.28x = 1,912.57 × 818.99
4. Step 4: Simplify right side
   1,386.28x = 1,566,372.95
5. Step 5: Solve for x
   x = 1,566,372.95/1,386.28
6. Step 6: Final answer
   x = 1,129.91