Finding the Fourth Proportional to 1,569.59, 2,355.60 and 839.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,569.59 : 2,355.60 = 839.78 : x
2. Step 2: Convert to fraction form
   1,569.59/2,355.60 = 839.78/x
3. Step 3: Cross multiply
   1,569.59x = 2,355.60 × 839.78
4. Step 4: Simplify right side
   1,569.59x = 1,978,185.77
5. Step 5: Solve for x
   x = 1,978,185.77/1,569.59
6. Step 6: Final answer
   x = 1,260.32