Finding the Fourth Proportional to 1,212.56, 1,673.50 and 688.60

Step by Step Solution

1. Step 1: Write the proportion equation
   1,212.56 : 1,673.50 = 688.60 : x
2. Step 2: Convert to fraction form
   1,212.56/1,673.50 = 688.60/x
3. Step 3: Cross multiply
   1,212.56x = 1,673.50 × 688.60
4. Step 4: Simplify right side
   1,212.56x = 1,152,372.10
5. Step 5: Solve for x
   x = 1,152,372.10/1,212.56
6. Step 6: Final answer
   x = 950.36