Finding the Fourth Proportional to 78.86, 108.72 and 54.30

Step by Step Solution

1. Step 1: Write the proportion equation
   78.86 : 108.72 = 54.30 : x
2. Step 2: Convert to fraction form
   78.86/108.72 = 54.30/x
3. Step 3: Cross multiply
   78.86x = 108.72 × 54.30
4. Step 4: Simplify right side
   78.86x = 5,903.50
5. Step 5: Solve for x
   x = 5,903.50/78.86
6. Step 6: Final answer
   x = 74.86