Finding the Fourth Proportional to 111.38, 153.78 and 78.71

Step by Step Solution

1. Step 1: Write the proportion equation
   111.38 : 153.78 = 78.71 : x
2. Step 2: Convert to fraction form
   111.38/153.78 = 78.71/x
3. Step 3: Cross multiply
   111.38x = 153.78 × 78.71
4. Step 4: Simplify right side
   111.38x = 12,104.02
5. Step 5: Solve for x
   x = 12,104.02/111.38
6. Step 6: Final answer
   x = 108.67