Finding the Fourth Proportional to 1,288.76, 1,778.50 and 699.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,288.76 : 1,778.50 = 699.31 : x
2. Step 2: Convert to fraction form
   1,288.76/1,778.50 = 699.31/x
3. Step 3: Cross multiply
   1,288.76x = 1,778.50 × 699.31
4. Step 4: Simplify right side
   1,288.76x = 1,243,725.93
5. Step 5: Solve for x
   x = 1,243,725.93/1,288.76
6. Step 6: Final answer
   x = 965.06