Finding the Fourth Proportional to 2,100.08, 3,150.48 and 639.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,100.08 : 3,150.48 = 639.20 : x
2. Step 2: Convert to fraction form
   2,100.08/3,150.48 = 639.20/x
3. Step 3: Cross multiply
   2,100.08x = 3,150.48 × 639.20
4. Step 4: Simplify right side
   2,100.08x = 2,013,786.82
5. Step 5: Solve for x
   x = 2,013,786.82/2,100.08
6. Step 6: Final answer
   x = 958.91