Finding the Fourth Proportional to 2,100.77, 3,151.19 and 639.94

Step by Step Solution

1. Step 1: Write the proportion equation
   2,100.77 : 3,151.19 = 639.94 : x
2. Step 2: Convert to fraction form
   2,100.77/3,151.19 = 639.94/x
3. Step 3: Cross multiply
   2,100.77x = 3,151.19 × 639.94
4. Step 4: Simplify right side
   2,100.77x = 2,016,572.53
5. Step 5: Solve for x
   x = 2,016,572.53/2,100.77
6. Step 6: Final answer
   x = 959.92