Finding the Fourth Proportional to 2,101.93, 3,151.87 and 640.69

Step by Step Solution

1. Step 1: Write the proportion equation
   2,101.93 : 3,151.87 = 640.69 : x
2. Step 2: Convert to fraction form
   2,101.93/3,151.87 = 640.69/x
3. Step 3: Cross multiply
   2,101.93x = 3,151.87 × 640.69
4. Step 4: Simplify right side
   2,101.93x = 2,019,371.59
5. Step 5: Solve for x
   x = 2,019,371.59/2,101.93
6. Step 6: Final answer
   x = 960.72