Finding the Fourth Proportional to 128.18, 176.86 and 72.91

Step by Step Solution

1. Step 1: Write the proportion equation
   128.18 : 176.86 = 72.91 : x
2. Step 2: Convert to fraction form
   128.18/176.86 = 72.91/x
3. Step 3: Cross multiply
   128.18x = 176.86 × 72.91
4. Step 4: Simplify right side
   128.18x = 12,894.86
5. Step 5: Solve for x
   x = 12,894.86/128.18
6. Step 6: Final answer
   x = 100.60