Finding the Fourth Proportional to 111.56, 153.96 and 78.80

Step by Step Solution

1. Step 1: Write the proportion equation
   111.56 : 153.96 = 78.80 : x
2. Step 2: Convert to fraction form
   111.56/153.96 = 78.80/x
3. Step 3: Cross multiply
   111.56x = 153.96 × 78.80
4. Step 4: Simplify right side
   111.56x = 12,132.05
5. Step 5: Solve for x
   x = 12,132.05/111.56
6. Step 6: Final answer
   x = 108.75