Finding the Fourth Proportional to 2,012.78, 3,019.56 and 858.50

Step by Step Solution

1. Step 1: Write the proportion equation
   2,012.78 : 3,019.56 = 858.50 : x
2. Step 2: Convert to fraction form
   2,012.78/3,019.56 = 858.50/x
3. Step 3: Cross multiply
   2,012.78x = 3,019.56 × 858.50
4. Step 4: Simplify right side
   2,012.78x = 2,592,292.26
5. Step 5: Solve for x
   x = 2,592,292.26/2,012.78
6. Step 6: Final answer
   x = 1,287.92