Finding the Fourth Proportional to 1,223.57, 1,688.52 and 699.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,223.57 : 1,688.52 = 699.61 : x
2. Step 2: Convert to fraction form
   1,223.57/1,688.52 = 699.61/x
3. Step 3: Cross multiply
   1,223.57x = 1,688.52 × 699.61
4. Step 4: Simplify right side
   1,223.57x = 1,181,297.03
5. Step 5: Solve for x
   x = 1,181,297.03/1,223.57
6. Step 6: Final answer
   x = 965.46