Finding the Fourth Proportional to 82.98, 123.78 and 81.15

Step by Step Solution

1. Step 1: Write the proportion equation
   82.98 : 123.78 = 81.15 : x
2. Step 2: Convert to fraction form
   82.98/123.78 = 81.15/x
3. Step 3: Cross multiply
   82.98x = 123.78 × 81.15
4. Step 4: Simplify right side
   82.98x = 10,044.75
5. Step 5: Solve for x
   x = 10,044.75/82.98
6. Step 6: Final answer
   x = 121.05