Finding the Fourth Proportional to 128.38, 177.15 and 72.37

Step by Step Solution

1. Step 1: Write the proportion equation
   128.38 : 177.15 = 72.37 : x
2. Step 2: Convert to fraction form
   128.38/177.15 = 72.37/x
3. Step 3: Cross multiply
   128.38x = 177.15 × 72.37
4. Step 4: Simplify right side
   128.38x = 12,819.57
5. Step 5: Solve for x
   x = 12,819.57/128.38
6. Step 6: Final answer
   x = 99.86