Finding the Fourth Proportional to 1,311.16, 1,809.06 and 780.01

Step by Step Solution

1. Step 1: Write the proportion equation
   1,311.16 : 1,809.06 = 780.01 : x
2. Step 2: Convert to fraction form
   1,311.16/1,809.06 = 780.01/x
3. Step 3: Cross multiply
   1,311.16x = 1,809.06 × 780.01
4. Step 4: Simplify right side
   1,311.16x = 1,411,084.89
5. Step 5: Solve for x
   x = 1,411,084.89/1,311.16
6. Step 6: Final answer
   x = 1,076.21