Finding the Fourth Proportional to 1,123.16, 1,683.78 and 661.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,123.16 : 1,683.78 = 661.40 : x
2. Step 2: Convert to fraction form
   1,123.16/1,683.78 = 661.40/x
3. Step 3: Cross multiply
   1,123.16x = 1,683.78 × 661.40
4. Step 4: Simplify right side
   1,123.16x = 1,113,652.09
5. Step 5: Solve for x
   x = 1,113,652.09/1,123.16
6. Step 6: Final answer
   x = 991.53