Finding the Fourth Proportional to 875.31, 1,311.42 and 779.98

Step by Step Solution

1. Step 1: Write the proportion equation
   875.31 : 1,311.42 = 779.98 : x
2. Step 2: Convert to fraction form
   875.31/1,311.42 = 779.98/x
3. Step 3: Cross multiply
   875.31x = 1,311.42 × 779.98
4. Step 4: Simplify right side
   875.31x = 1,022,883.48
5. Step 5: Solve for x
   x = 1,022,883.48/875.31
6. Step 6: Final answer
   x = 1,168.59