Finding the Fourth Proportional to 105.12, 144.90 and 90.42

Step by Step Solution

1. Step 1: Write the proportion equation
   105.12 : 144.90 = 90.42 : x
2. Step 2: Convert to fraction form
   105.12/144.90 = 90.42/x
3. Step 3: Cross multiply
   105.12x = 144.90 × 90.42
4. Step 4: Simplify right side
   105.12x = 13,101.86
5. Step 5: Solve for x
   x = 13,101.86/105.12
6. Step 6: Final answer
   x = 124.64