Finding the Fourth Proportional to 128.56, 191.90 and 111.55

Step by Step Solution

1. Step 1: Write the proportion equation
   128.56 : 191.90 = 111.55 : x
2. Step 2: Convert to fraction form
   128.56/191.90 = 111.55/x
3. Step 3: Cross multiply
   128.56x = 191.90 × 111.55
4. Step 4: Simplify right side
   128.56x = 21,406.45
5. Step 5: Solve for x
   x = 21,406.45/128.56
6. Step 6: Final answer
   x = 166.51