Finding the Fourth Proportional to 80.98, 111.78 and 64.72

Step by Step Solution

1. Step 1: Write the proportion equation
   80.98 : 111.78 = 64.72 : x
2. Step 2: Convert to fraction form
   80.98/111.78 = 64.72/x
3. Step 3: Cross multiply
   80.98x = 111.78 × 64.72
4. Step 4: Simplify right side
   80.98x = 7,234.40
5. Step 5: Solve for x
   x = 7,234.40/80.98
6. Step 6: Final answer
   x = 89.34