Finding the Fourth Proportional to 78.39, 108.15 and 53.89

Step by Step Solution

1. Step 1: Write the proportion equation
   78.39 : 108.15 = 53.89 : x
2. Step 2: Convert to fraction form
   78.39/108.15 = 53.89/x
3. Step 3: Cross multiply
   78.39x = 108.15 × 53.89
4. Step 4: Simplify right side
   78.39x = 5,828.20
5. Step 5: Solve for x
   x = 5,828.20/78.39
6. Step 6: Final answer
   x = 74.35