Finding the Fourth Proportional to 187.72, 258.89 and 128.59

Step by Step Solution

1. Step 1: Write the proportion equation
   187.72 : 258.89 = 128.59 : x
2. Step 2: Convert to fraction form
   187.72/258.89 = 128.59/x
3. Step 3: Cross multiply
   187.72x = 258.89 × 128.59
4. Step 4: Simplify right side
   187.72x = 33,289.37
5. Step 5: Solve for x
   x = 33,289.37/187.72
6. Step 6: Final answer
   x = 177.34