Finding the Fourth Proportional to 128.12, 191.18 and 111.72

Step by Step Solution

1. Step 1: Write the proportion equation
   128.12 : 191.18 = 111.72 : x
2. Step 2: Convert to fraction form
   128.12/191.18 = 111.72/x
3. Step 3: Cross multiply
   128.12x = 191.18 × 111.72
4. Step 4: Simplify right side
   128.12x = 21,358.63
5. Step 5: Solve for x
   x = 21,358.63/128.12
6. Step 6: Final answer
   x = 166.71