Finding the Fourth Proportional to 2,100.71, 3,151.25 and 639.88

Step by Step Solution

1. Step 1: Write the proportion equation
   2,100.71 : 3,151.25 = 639.88 : x
2. Step 2: Convert to fraction form
   2,100.71/3,151.25 = 639.88/x
3. Step 3: Cross multiply
   2,100.71x = 3,151.25 × 639.88
4. Step 4: Simplify right side
   2,100.71x = 2,016,410.77
5. Step 5: Solve for x
   x = 2,016,410.77/2,100.71
6. Step 6: Final answer
   x = 959.87