Finding the Fourth Proportional to 111.51, 153.72 and 78.66

Step by Step Solution

1. Step 1: Write the proportion equation
   111.51 : 153.72 = 78.66 : x
2. Step 2: Convert to fraction form
   111.51/153.72 = 78.66/x
3. Step 3: Cross multiply
   111.51x = 153.72 × 78.66
4. Step 4: Simplify right side
   111.51x = 12,091.62
5. Step 5: Solve for x
   x = 12,091.62/111.51
6. Step 6: Final answer
   x = 108.44