Finding the Fourth Proportional to 105.72, 145.90 and 72.96

Step by Step Solution

1. Step 1: Write the proportion equation
   105.72 : 145.90 = 72.96 : x
2. Step 2: Convert to fraction form
   105.72/145.90 = 72.96/x
3. Step 3: Cross multiply
   105.72x = 145.90 × 72.96
4. Step 4: Simplify right side
   105.72x = 10,644.86
5. Step 5: Solve for x
   x = 10,644.86/105.72
6. Step 6: Final answer
   x = 100.69