Finding the Fourth Proportional to 1,212.09, 1,672.56 and 688.02

Step by Step Solution

1. Step 1: Write the proportion equation
   1,212.09 : 1,672.56 = 688.02 : x
2. Step 2: Convert to fraction form
   1,212.09/1,672.56 = 688.02/x
3. Step 3: Cross multiply
   1,212.09x = 1,672.56 × 688.02
4. Step 4: Simplify right side
   1,212.09x = 1,150,754.73
5. Step 5: Solve for x
   x = 1,150,754.73/1,212.09
6. Step 6: Final answer
   x = 949.40