Finding the Fourth Proportional to 78.72, 108.62 and 54.15

Step by Step Solution

1. Step 1: Write the proportion equation
   78.72 : 108.62 = 54.15 : x
2. Step 2: Convert to fraction form
   78.72/108.62 = 54.15/x
3. Step 3: Cross multiply
   78.72x = 108.62 × 54.15
4. Step 4: Simplify right side
   78.72x = 5,881.50
5. Step 5: Solve for x
   x = 5,881.50/78.72
6. Step 6: Final answer
   x = 74.71