Finding the Fourth Proportional to 78.88, 108.72 and 65.92

Step by Step Solution

1. Step 1: Write the proportion equation
   78.88 : 108.72 = 65.92 : x
2. Step 2: Convert to fraction form
   78.88/108.72 = 65.92/x
3. Step 3: Cross multiply
   78.88x = 108.72 × 65.92
4. Step 4: Simplify right side
   78.88x = 7,166.82
5. Step 5: Solve for x
   x = 7,166.82/78.88
6. Step 6: Final answer
   x = 90.86