Finding the Fourth Proportional to 116.72, 160.91 and 81.78

Step by Step Solution

1. Step 1: Write the proportion equation
   116.72 : 160.91 = 81.78 : x
2. Step 2: Convert to fraction form
   116.72/160.91 = 81.78/x
3. Step 3: Cross multiply
   116.72x = 160.91 × 81.78
4. Step 4: Simplify right side
   116.72x = 13,160.10
5. Step 5: Solve for x
   x = 13,160.10/116.72
6. Step 6: Final answer
   x = 112.75