Finding the Fourth Proportional to 142.48, 196.20 and 128.72

Step by Step Solution

1. Step 1: Write the proportion equation
   142.48 : 196.20 = 128.72 : x
2. Step 2: Convert to fraction form
   142.48/196.20 = 128.72/x
3. Step 3: Cross multiply
   142.48x = 196.20 × 128.72
4. Step 4: Simplify right side
   142.48x = 25,254.86
5. Step 5: Solve for x
   x = 25,254.86/142.48
6. Step 6: Final answer
   x = 177.25