Finding the Fourth Proportional to 142.42, 196.62 and 128.56

Step by Step Solution

1. Step 1: Write the proportion equation
   142.42 : 196.62 = 128.56 : x
2. Step 2: Convert to fraction form
   142.42/196.62 = 128.56/x
3. Step 3: Cross multiply
   142.42x = 196.62 × 128.56
4. Step 4: Simplify right side
   142.42x = 25,277.47
5. Step 5: Solve for x
   x = 25,277.47/142.42
6. Step 6: Final answer
   x = 177.49