Finding the Fourth Proportional to 105.15, 145.09 and 72.42

Step by Step Solution

1. Step 1: Write the proportion equation
   105.15 : 145.09 = 72.42 : x
2. Step 2: Convert to fraction form
   105.15/145.09 = 72.42/x
3. Step 3: Cross multiply
   105.15x = 145.09 × 72.42
4. Step 4: Simplify right side
   105.15x = 10,507.42
5. Step 5: Solve for x
   x = 10,507.42/105.15
6. Step 6: Final answer
   x = 99.93