Finding the Fourth Proportional to 111.10, 166.71 and 78.61

Step by Step Solution

1. Step 1: Write the proportion equation
   111.10 : 166.71 = 78.61 : x
2. Step 2: Convert to fraction form
   111.10/166.71 = 78.61/x
3. Step 3: Cross multiply
   111.10x = 166.71 × 78.61
4. Step 4: Simplify right side
   111.10x = 13,105.07
5. Step 5: Solve for x
   x = 13,105.07/111.10
6. Step 6: Final answer
   x = 117.96