Finding the Fourth Proportional to 105.16, 145.09 and 72.42

Step by Step Solution

1. Step 1: Write the proportion equation
   105.16 : 145.09 = 72.42 : x
2. Step 2: Convert to fraction form
   105.16/145.09 = 72.42/x
3. Step 3: Cross multiply
   105.16x = 145.09 × 72.42
4. Step 4: Simplify right side
   105.16x = 10,507.24
5. Step 5: Solve for x
   x = 10,507.24/105.16
6. Step 6: Final answer
   x = 99.92