Finding the Fourth Proportional to 105.25, 145.34 and 80.42

Step by Step Solution

1. Step 1: Write the proportion equation
   105.25 : 145.34 = 80.42 : x
2. Step 2: Convert to fraction form
   105.25/145.34 = 80.42/x
3. Step 3: Cross multiply
   105.25x = 145.34 × 80.42
4. Step 4: Simplify right side
   105.25x = 11,688.28
5. Step 5: Solve for x
   x = 11,688.28/105.25
6. Step 6: Final answer
   x = 111.05