Finding the Fourth Proportional to 2,100.66, 3,151.05 and 639.81

Step by Step Solution

1. Step 1: Write the proportion equation
   2,100.66 : 3,151.05 = 639.81 : x
2. Step 2: Convert to fraction form
   2,100.66/3,151.05 = 639.81/x
3. Step 3: Cross multiply
   2,100.66x = 3,151.05 × 639.81
4. Step 4: Simplify right side
   2,100.66x = 2,016,073.30
5. Step 5: Solve for x
   x = 2,016,073.30/2,100.66
6. Step 6: Final answer
   x = 959.73