Finding the Fourth Proportional to 82.86, 124.21 and 81.78

Step by Step Solution

1. Step 1: Write the proportion equation
   82.86 : 124.21 = 81.78 : x
2. Step 2: Convert to fraction form
   82.86/124.21 = 81.78/x
3. Step 3: Cross multiply
   82.86x = 124.21 × 81.78
4. Step 4: Simplify right side
   82.86x = 10,157.89
5. Step 5: Solve for x
   x = 10,157.89/82.86
6. Step 6: Final answer
   x = 122.59