Finding the Fourth Proportional to 1,013.72, 1,399.10 and 620.96

Step by Step Solution

1. Step 1: Write the proportion equation
   1,013.72 : 1,399.10 = 620.96 : x
2. Step 2: Convert to fraction form
   1,013.72/1,399.10 = 620.96/x
3. Step 3: Cross multiply
   1,013.72x = 1,399.10 × 620.96
4. Step 4: Simplify right side
   1,013.72x = 868,785.14
5. Step 5: Solve for x
   x = 868,785.14/1,013.72
6. Step 6: Final answer
   x = 857.03