Finding the Fourth Proportional to 1,205.78, 1,664.46 and 786.49

Step by Step Solution

1. Step 1: Write the proportion equation
   1,205.78 : 1,664.46 = 786.49 : x
2. Step 2: Convert to fraction form
   1,205.78/1,664.46 = 786.49/x
3. Step 3: Cross multiply
   1,205.78x = 1,664.46 × 786.49
4. Step 4: Simplify right side
   1,205.78x = 1,309,068.89
5. Step 5: Solve for x
   x = 1,309,068.89/1,205.78
6. Step 6: Final answer
   x = 1,085.66