Finding the Fourth Proportional to 1,211.69, 1,672.10 and 687.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,211.69 : 1,672.10 = 687.72 : x
2. Step 2: Convert to fraction form
   1,211.69/1,672.10 = 687.72/x
3. Step 3: Cross multiply
   1,211.69x = 1,672.10 × 687.72
4. Step 4: Simplify right side
   1,211.69x = 1,149,936.61
5. Step 5: Solve for x
   x = 1,149,936.61/1,211.69
6. Step 6: Final answer
   x = 949.04