Finding the Fourth Proportional to 71.31, 106.86 and 54.15

Step by Step Solution

1. Step 1: Write the proportion equation
   71.31 : 106.86 = 54.15 : x
2. Step 2: Convert to fraction form
   71.31/106.86 = 54.15/x
3. Step 3: Cross multiply
   71.31x = 106.86 × 54.15
4. Step 4: Simplify right side
   71.31x = 5,786.47
5. Step 5: Solve for x
   x = 5,786.47/71.31
6. Step 6: Final answer
   x = 81.15