Finding the Fourth Proportional to 78.77, 108.89 and 65.10

Step by Step Solution

1. Step 1: Write the proportion equation
   78.77 : 108.89 = 65.10 : x
2. Step 2: Convert to fraction form
   78.77/108.89 = 65.10/x
3. Step 3: Cross multiply
   78.77x = 108.89 × 65.10
4. Step 4: Simplify right side
   78.77x = 7,089.43
5. Step 5: Solve for x
   x = 7,089.43/78.77
6. Step 6: Final answer
   x = 90.00