Finding the Fourth Proportional to 1,638.05, 2,454.90 and 858.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,638.05 : 2,454.90 = 858.72 : x
2. Step 2: Convert to fraction form
   1,638.05/2,454.90 = 858.72/x
3. Step 3: Cross multiply
   1,638.05x = 2,454.90 × 858.72
4. Step 4: Simplify right side
   1,638.05x = 2,108,059.45
5. Step 5: Solve for x
   x = 2,108,059.45/1,638.05
6. Step 6: Final answer
   x = 1,286.93