Finding the Fourth Proportional to 128.02, 176.72 and 78.21

Step by Step Solution

1. Step 1: Write the proportion equation
   128.02 : 176.72 = 78.21 : x
2. Step 2: Convert to fraction form
   128.02/176.72 = 78.21/x
3. Step 3: Cross multiply
   128.02x = 176.72 × 78.21
4. Step 4: Simplify right side
   128.02x = 13,821.27
5. Step 5: Solve for x
   x = 13,821.27/128.02
6. Step 6: Final answer
   x = 107.96