Finding the Fourth Proportional to 105.17, 145.17 and 72.43

Step by Step Solution

1. Step 1: Write the proportion equation
   105.17 : 145.17 = 72.43 : x
2. Step 2: Convert to fraction form
   105.17/145.17 = 72.43/x
3. Step 3: Cross multiply
   105.17x = 145.17 × 72.43
4. Step 4: Simplify right side
   105.17x = 10,514.30
5. Step 5: Solve for x
   x = 10,514.30/105.17
6. Step 6: Final answer
   x = 99.98