Finding the Fourth Proportional to 78.69, 108.63 and 54.20

Step by Step Solution

1. Step 1: Write the proportion equation
   78.69 : 108.63 = 54.20 : x
2. Step 2: Convert to fraction form
   78.69/108.63 = 54.20/x
3. Step 3: Cross multiply
   78.69x = 108.63 × 54.20
4. Step 4: Simplify right side
   78.69x = 5,888.02
5. Step 5: Solve for x
   x = 5,888.02/78.69
6. Step 6: Final answer
   x = 74.82