Finding the Fourth Proportional to 128.37, 192.39 and 56.15

Step by Step Solution

1. Step 1: Write the proportion equation
   128.37 : 192.39 = 56.15 : x
2. Step 2: Convert to fraction form
   128.37/192.39 = 56.15/x
3. Step 3: Cross multiply
   128.37x = 192.39 × 56.15
4. Step 4: Simplify right side
   128.37x = 10,802.70
5. Step 5: Solve for x
   x = 10,802.70/128.37
6. Step 6: Final answer
   x = 84.15