Finding the Fourth Proportional to 128.80, 193.27 and 42.15

Step by Step Solution

1. Step 1: Write the proportion equation
   128.80 : 193.27 = 42.15 : x
2. Step 2: Convert to fraction form
   128.80/193.27 = 42.15/x
3. Step 3: Cross multiply
   128.80x = 193.27 × 42.15
4. Step 4: Simplify right side
   128.80x = 8,146.33
5. Step 5: Solve for x
   x = 8,146.33/128.80
6. Step 6: Final answer
   x = 63.25