Finding the Fourth Proportional to 111.16, 166.38 and 78.58

Step by Step Solution

1. Step 1: Write the proportion equation
   111.16 : 166.38 = 78.58 : x
2. Step 2: Convert to fraction form
   111.16/166.38 = 78.58/x
3. Step 3: Cross multiply
   111.16x = 166.38 × 78.58
4. Step 4: Simplify right side
   111.16x = 13,074.14
5. Step 5: Solve for x
   x = 13,074.14/111.16
6. Step 6: Final answer
   x = 117.62