Finding the Fourth Proportional to 81.24, 121.86 and 42.72

Step by Step Solution

1. Step 1: Write the proportion equation
   81.24 : 121.86 = 42.72 : x
2. Step 2: Convert to fraction form
   81.24/121.86 = 42.72/x
3. Step 3: Cross multiply
   81.24x = 121.86 × 42.72
4. Step 4: Simplify right side
   81.24x = 5,205.86
5. Step 5: Solve for x
   x = 5,205.86/81.24
6. Step 6: Final answer
   x = 64.08