Finding the Fourth Proportional to 82.72, 123.60 and 81.28

Step by Step Solution

1. Step 1: Write the proportion equation
   82.72 : 123.60 = 81.28 : x
2. Step 2: Convert to fraction form
   82.72/123.60 = 81.28/x
3. Step 3: Cross multiply
   82.72x = 123.60 × 81.28
4. Step 4: Simplify right side
   82.72x = 10,046.21
5. Step 5: Solve for x
   x = 10,046.21/82.72
6. Step 6: Final answer
   x = 121.45