Finding the Fourth Proportional to 105.28, 145.12 and 72.48

Step by Step Solution

1. Step 1: Write the proportion equation
   105.28 : 145.12 = 72.48 : x
2. Step 2: Convert to fraction form
   105.28/145.12 = 72.48/x
3. Step 3: Cross multiply
   105.28x = 145.12 × 72.48
4. Step 4: Simplify right side
   105.28x = 10,518.30
5. Step 5: Solve for x
   x = 10,518.30/105.28
6. Step 6: Final answer
   x = 99.91