Finding the Fourth Proportional to 1,223.10, 1,687.59 and 699.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,223.10 : 1,687.59 = 699.30 : x
2. Step 2: Convert to fraction form
   1,223.10/1,687.59 = 699.30/x
3. Step 3: Cross multiply
   1,223.10x = 1,687.59 × 699.30
4. Step 4: Simplify right side
   1,223.10x = 1,180,131.69
5. Step 5: Solve for x
   x = 1,180,131.69/1,223.10
6. Step 6: Final answer
   x = 964.87