Finding the Fourth Proportional to 1,278.89, 1,764.56 and 858.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,278.89 : 1,764.56 = 858.50 : x
2. Step 2: Convert to fraction form
   1,278.89/1,764.56 = 858.50/x
3. Step 3: Cross multiply
   1,278.89x = 1,764.56 × 858.50
4. Step 4: Simplify right side
   1,278.89x = 1,514,870.47
5. Step 5: Solve for x
   x = 1,514,870.47/1,278.89
6. Step 6: Final answer
   x = 1,184.52