Finding the Fourth Proportional to 111.29, 153.65 and 78.15

Step by Step Solution

1. Step 1: Write the proportion equation
   111.29 : 153.65 = 78.15 : x
2. Step 2: Convert to fraction form
   111.29/153.65 = 78.15/x
3. Step 3: Cross multiply
   111.29x = 153.65 × 78.15
4. Step 4: Simplify right side
   111.29x = 12,007.36
5. Step 5: Solve for x
   x = 12,007.36/111.29
6. Step 6: Final answer
   x = 107.90