Finding the Fourth Proportional to 86.78, 119.83 and 65.05

Step by Step Solution

1. Step 1: Write the proportion equation
   86.78 : 119.83 = 65.05 : x
2. Step 2: Convert to fraction form
   86.78/119.83 = 65.05/x
3. Step 3: Cross multiply
   86.78x = 119.83 × 65.05
4. Step 4: Simplify right side
   86.78x = 7,794.94
5. Step 5: Solve for x
   x = 7,794.94/86.78
6. Step 6: Final answer
   x = 89.82