Finding the Fourth Proportional to 1,288.77, 1,778.51 and 699.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,288.77 : 1,778.51 = 699.31 : x
2. Step 2: Convert to fraction form
   1,288.77/1,778.51 = 699.31/x
3. Step 3: Cross multiply
   1,288.77x = 1,778.51 × 699.31
4. Step 4: Simplify right side
   1,288.77x = 1,243,729.83
5. Step 5: Solve for x
   x = 1,243,729.83/1,288.77
6. Step 6: Final answer
   x = 965.05