Finding the Fourth Proportional to 105.12, 145.01 and 72.31

Step by Step Solution

1. Step 1: Write the proportion equation
   105.12 : 145.01 = 72.31 : x
2. Step 2: Convert to fraction form
   105.12/145.01 = 72.31/x
3. Step 3: Cross multiply
   105.12x = 145.01 × 72.31
4. Step 4: Simplify right side
   105.12x = 10,485.67
5. Step 5: Solve for x
   x = 10,485.67/105.12
6. Step 6: Final answer
   x = 99.75