Finding the Fourth Proportional to 82.18, 123.91 and 81.29

Step by Step Solution

1. Step 1: Write the proportion equation
   82.18 : 123.91 = 81.29 : x
2. Step 2: Convert to fraction form
   82.18/123.91 = 81.29/x
3. Step 3: Cross multiply
   82.18x = 123.91 × 81.29
4. Step 4: Simplify right side
   82.18x = 10,072.24
5. Step 5: Solve for x
   x = 10,072.24/82.18
6. Step 6: Final answer
   x = 122.57