Finding the Fourth Proportional to 131.91, 196.31 and 128.28

Step by Step Solution

1. Step 1: Write the proportion equation
   131.91 : 196.31 = 128.28 : x
2. Step 2: Convert to fraction form
   131.91/196.31 = 128.28/x
3. Step 3: Cross multiply
   131.91x = 196.31 × 128.28
4. Step 4: Simplify right side
   131.91x = 25,182.01
5. Step 5: Solve for x
   x = 25,182.01/131.91
6. Step 6: Final answer
   x = 190.90