Finding the Fourth Proportional to 1,311.54, 1,809.57 and 780.27

Step by Step Solution

1. Step 1: Write the proportion equation
   1,311.54 : 1,809.57 = 780.27 : x
2. Step 2: Convert to fraction form
   1,311.54/1,809.57 = 780.27/x
3. Step 3: Cross multiply
   1,311.54x = 1,809.57 × 780.27
4. Step 4: Simplify right side
   1,311.54x = 1,411,953.18
5. Step 5: Solve for x
   x = 1,411,953.18/1,311.54
6. Step 6: Final answer
   x = 1,076.56