Finding the Fourth Proportional to 111.64, 153.90 and 78.88

Step by Step Solution

1. Step 1: Write the proportion equation
   111.64 : 153.90 = 78.88 : x
2. Step 2: Convert to fraction form
   111.64/153.90 = 78.88/x
3. Step 3: Cross multiply
   111.64x = 153.90 × 78.88
4. Step 4: Simplify right side
   111.64x = 12,139.63
5. Step 5: Solve for x
   x = 12,139.63/111.64
6. Step 6: Final answer
   x = 108.74