Finding the Fourth Proportional to 78.72, 108.58 and 54.12

Step by Step Solution

1. Step 1: Write the proportion equation
   78.72 : 108.58 = 54.12 : x
2. Step 2: Convert to fraction form
   78.72/108.58 = 54.12/x
3. Step 3: Cross multiply
   78.72x = 108.58 × 54.12
4. Step 4: Simplify right side
   78.72x = 5,876.35
5. Step 5: Solve for x
   x = 5,876.35/78.72
6. Step 6: Final answer
   x = 74.65