Finding the Fourth Proportional to 78.71, 108.71 and 54.20

Step by Step Solution

1. Step 1: Write the proportion equation
   78.71 : 108.71 = 54.20 : x
2. Step 2: Convert to fraction form
   78.71/108.71 = 54.20/x
3. Step 3: Cross multiply
   78.71x = 108.71 × 54.20
4. Step 4: Simplify right side
   78.71x = 5,892.29
5. Step 5: Solve for x
   x = 5,892.29/78.71
6. Step 6: Final answer
   x = 74.87