Finding the Fourth Proportional to 128.61, 191.69 and 128.42

Step by Step Solution

1. Step 1: Write the proportion equation
   128.61 : 191.69 = 128.42 : x
2. Step 2: Convert to fraction form
   128.61/191.69 = 128.42/x
3. Step 3: Cross multiply
   128.61x = 191.69 × 128.42
4. Step 4: Simplify right side
   128.61x = 24,615.23
5. Step 5: Solve for x
   x = 24,615.23/128.61
6. Step 6: Final answer
   x = 191.39