Finding the Fourth Proportional to 111.70, 154.06 and 80.72

Step by Step Solution

1. Step 1: Write the proportion equation
   111.70 : 154.06 = 80.72 : x
2. Step 2: Convert to fraction form
   111.70/154.06 = 80.72/x
3. Step 3: Cross multiply
   111.70x = 154.06 × 80.72
4. Step 4: Simplify right side
   111.70x = 12,435.54
5. Step 5: Solve for x
   x = 12,435.54/111.70
6. Step 6: Final answer
   x = 111.33