Finding the Fourth Proportional to 121.55, 167.72 and 72.42

Step by Step Solution

1. Step 1: Write the proportion equation
   121.55 : 167.72 = 72.42 : x
2. Step 2: Convert to fraction form
   121.55/167.72 = 72.42/x
3. Step 3: Cross multiply
   121.55x = 167.72 × 72.42
4. Step 4: Simplify right side
   121.55x = 12,145.44
5. Step 5: Solve for x
   x = 12,145.44/121.55
6. Step 6: Final answer
   x = 99.93