Finding the Fourth Proportional to 1,639.91, 2,458.72 and 817.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,639.91 : 2,458.72 = 817.61 : x
2. Step 2: Convert to fraction form
   1,639.91/2,458.72 = 817.61/x
3. Step 3: Cross multiply
   1,639.91x = 2,458.72 × 817.61
4. Step 4: Simplify right side
   1,639.91x = 2,010,269.97
5. Step 5: Solve for x
   x = 2,010,269.97/1,639.91
6. Step 6: Final answer
   x = 1,225.84