Finding the Fourth Proportional to 111.18, 153.36 and 78.42

Step by Step Solution

1. Step 1: Write the proportion equation
   111.18 : 153.36 = 78.42 : x
2. Step 2: Convert to fraction form
   111.18/153.36 = 78.42/x
3. Step 3: Cross multiply
   111.18x = 153.36 × 78.42
4. Step 4: Simplify right side
   111.18x = 12,026.49
5. Step 5: Solve for x
   x = 12,026.49/111.18
6. Step 6: Final answer
   x = 108.17