Finding the Fourth Proportional to 111.50, 153.20 and 90.72

Step by Step Solution

1. Step 1: Write the proportion equation
   111.50 : 153.20 = 90.72 : x
2. Step 2: Convert to fraction form
   111.50/153.20 = 90.72/x
3. Step 3: Cross multiply
   111.50x = 153.20 × 90.72
4. Step 4: Simplify right side
   111.50x = 13,898.53
5. Step 5: Solve for x
   x = 13,898.53/111.50
6. Step 6: Final answer
   x = 124.66