Finding the Fourth Proportional to 1,223.04, 1,687.68 and 990.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,223.04 : 1,687.68 = 990.72 : x
2. Step 2: Convert to fraction form
   1,223.04/1,687.68 = 990.72/x
3. Step 3: Cross multiply
   1,223.04x = 1,687.68 × 990.72
4. Step 4: Simplify right side
   1,223.04x = 1,672,018.33
5. Step 5: Solve for x
   x = 1,672,018.33/1,223.04
6. Step 6: Final answer
   x = 1,367.10