Finding the Fourth Proportional to 1,219.91, 1,683.46 and 660.38

Step by Step Solution

1. Step 1: Write the proportion equation
   1,219.91 : 1,683.46 = 660.38 : x
2. Step 2: Convert to fraction form
   1,219.91/1,683.46 = 660.38/x
3. Step 3: Cross multiply
   1,219.91x = 1,683.46 × 660.38
4. Step 4: Simplify right side
   1,219.91x = 1,111,715.72
5. Step 5: Solve for x
   x = 1,111,715.72/1,219.91
6. Step 6: Final answer
   x = 911.31