Finding the Fourth Proportional to 128.42, 192.72 and 99.60

Step by Step Solution

1. Step 1: Write the proportion equation
   128.42 : 192.72 = 99.60 : x
2. Step 2: Convert to fraction form
   128.42/192.72 = 99.60/x
3. Step 3: Cross multiply
   128.42x = 192.72 × 99.60
4. Step 4: Simplify right side
   128.42x = 19,194.91
5. Step 5: Solve for x
   x = 19,194.91/128.42
6. Step 6: Final answer
   x = 149.48