Finding the Fourth Proportional to 128.91, 193.38 and 56.76

Step by Step Solution

1. Step 1: Write the proportion equation
   128.91 : 193.38 = 56.76 : x
2. Step 2: Convert to fraction form
   128.91/193.38 = 56.76/x
3. Step 3: Cross multiply
   128.91x = 193.38 × 56.76
4. Step 4: Simplify right side
   128.91x = 10,976.25
5. Step 5: Solve for x
   x = 10,976.25/128.91
6. Step 6: Final answer
   x = 85.15