Finding the Fourth Proportional to 105.20, 145.02 and 72.39

Step by Step Solution

1. Step 1: Write the proportion equation
   105.20 : 145.02 = 72.39 : x
2. Step 2: Convert to fraction form
   105.20/145.02 = 72.39/x
3. Step 3: Cross multiply
   105.20x = 145.02 × 72.39
4. Step 4: Simplify right side
   105.20x = 10,498.00
5. Step 5: Solve for x
   x = 10,498.00/105.20
6. Step 6: Final answer
   x = 99.80