Finding the Fourth Proportional to 111.09, 166.50 and 105.15

Step by Step Solution

1. Step 1: Write the proportion equation
   111.09 : 166.50 = 105.15 : x
2. Step 2: Convert to fraction form
   111.09/166.50 = 105.15/x
3. Step 3: Cross multiply
   111.09x = 166.50 × 105.15
4. Step 4: Simplify right side
   111.09x = 17,507.48
5. Step 5: Solve for x
   x = 17,507.48/111.09
6. Step 6: Final answer
   x = 157.60