Finding the Fourth Proportional to 86.56, 129.72 and 78.96

Step by Step Solution

1. Step 1: Write the proportion equation
   86.56 : 129.72 = 78.96 : x
2. Step 2: Convert to fraction form
   86.56/129.72 = 78.96/x
3. Step 3: Cross multiply
   86.56x = 129.72 × 78.96
4. Step 4: Simplify right side
   86.56x = 10,242.69
5. Step 5: Solve for x
   x = 10,242.69/86.56
6. Step 6: Final answer
   x = 118.33