Finding the Fourth Proportional to 111.38, 153.57 and 86.78

Step by Step Solution

1. Step 1: Write the proportion equation
   111.38 : 153.57 = 86.78 : x
2. Step 2: Convert to fraction form
   111.38/153.57 = 86.78/x
3. Step 3: Cross multiply
   111.38x = 153.57 × 86.78
4. Step 4: Simplify right side
   111.38x = 13,326.37
5. Step 5: Solve for x
   x = 13,326.37/111.38
6. Step 6: Final answer
   x = 119.65