Finding the Fourth Proportional to 105.42, 145.31 and 83.55

Step by Step Solution

1. Step 1: Write the proportion equation
   105.42 : 145.31 = 83.55 : x
2. Step 2: Convert to fraction form
   105.42/145.31 = 83.55/x
3. Step 3: Cross multiply
   105.42x = 145.31 × 83.55
4. Step 4: Simplify right side
   105.42x = 12,140.23
5. Step 5: Solve for x
   x = 12,140.23/105.42
6. Step 6: Final answer
   x = 115.16