Finding the Fourth Proportional to 1,212.21, 1,672.91 and 688.29

Step by Step Solution

1. Step 1: Write the proportion equation
   1,212.21 : 1,672.91 = 688.29 : x
2. Step 2: Convert to fraction form
   1,212.21/1,672.91 = 688.29/x
3. Step 3: Cross multiply
   1,212.21x = 1,672.91 × 688.29
4. Step 4: Simplify right side
   1,212.21x = 1,151,443.78
5. Step 5: Solve for x
   x = 1,151,443.78/1,212.21
6. Step 6: Final answer
   x = 949.87