Finding the Fourth Proportional to 111.80, 154.21 and 72.42

Step by Step Solution

1. Step 1: Write the proportion equation
   111.80 : 154.21 = 72.42 : x
2. Step 2: Convert to fraction form
   111.80/154.21 = 72.42/x
3. Step 3: Cross multiply
   111.80x = 154.21 × 72.42
4. Step 4: Simplify right side
   111.80x = 11,167.89
5. Step 5: Solve for x
   x = 11,167.89/111.80
6. Step 6: Final answer
   x = 99.89