Finding the Fourth Proportional to 2,101.62, 3,152.49 and 640.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,101.62 : 3,152.49 = 640.78 : x
2. Step 2: Convert to fraction form
   2,101.62/3,152.49 = 640.78/x
3. Step 3: Cross multiply
   2,101.62x = 3,152.49 × 640.78
4. Step 4: Simplify right side
   2,101.62x = 2,020,036.78
5. Step 5: Solve for x
   x = 2,020,036.78/2,101.62
6. Step 6: Final answer
   x = 961.18