Finding the Fourth Proportional to 105.57, 145.53 and 90.18

Step by Step Solution

1. Step 1: Write the proportion equation
   105.57 : 145.53 = 90.18 : x
2. Step 2: Convert to fraction form
   105.57/145.53 = 90.18/x
3. Step 3: Cross multiply
   105.57x = 145.53 × 90.18
4. Step 4: Simplify right side
   105.57x = 13,123.90
5. Step 5: Solve for x
   x = 13,123.90/105.57
6. Step 6: Final answer
   x = 124.31