Finding the Fourth Proportional to 1,223.28, 1,688.10 and 699.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,223.28 : 1,688.10 = 699.30 : x
2. Step 2: Convert to fraction form
   1,223.28/1,688.10 = 699.30/x
3. Step 3: Cross multiply
   1,223.28x = 1,688.10 × 699.30
4. Step 4: Simplify right side
   1,223.28x = 1,180,488.33
5. Step 5: Solve for x
   x = 1,180,488.33/1,223.28
6. Step 6: Final answer
   x = 965.02