Finding the Fourth Proportional to 78.17, 107.78 and 65.10

Step by Step Solution

1. Step 1: Write the proportion equation
   78.17 : 107.78 = 65.10 : x
2. Step 2: Convert to fraction form
   78.17/107.78 = 65.10/x
3. Step 3: Cross multiply
   78.17x = 107.78 × 65.10
4. Step 4: Simplify right side
   78.17x = 7,016.15
5. Step 5: Solve for x
   x = 7,016.15/78.17
6. Step 6: Final answer
   x = 89.76