Finding the Fourth Proportional to 1,640.39, 2,458.28 and 1,085.74

Step by Step Solution

1. Step 1: Write the proportion equation
   1,640.39 : 2,458.28 = 1,085.74 : x
2. Step 2: Convert to fraction form
   1,640.39/2,458.28 = 1,085.74/x
3. Step 3: Cross multiply
   1,640.39x = 2,458.28 × 1,085.74
4. Step 4: Simplify right side
   1,640.39x = 2,669,049.50
5. Step 5: Solve for x
   x = 2,669,049.50/1,640.39
6. Step 6: Final answer
   x = 1,627.09