Finding the Fourth Proportional to 1,223.59, 1,688.56 and 699.63

Step by Step Solution

1. Step 1: Write the proportion equation
   1,223.59 : 1,688.56 = 699.63 : x
2. Step 2: Convert to fraction form
   1,223.59/1,688.56 = 699.63/x
3. Step 3: Cross multiply
   1,223.59x = 1,688.56 × 699.63
4. Step 4: Simplify right side
   1,223.59x = 1,181,367.23
5. Step 5: Solve for x
   x = 1,181,367.23/1,223.59
6. Step 6: Final answer
   x = 965.49