Finding the Fourth Proportional to 91.27, 136.17 and 78.28

Step by Step Solution

1. Step 1: Write the proportion equation
   91.27 : 136.17 = 78.28 : x
2. Step 2: Convert to fraction form
   91.27/136.17 = 78.28/x
3. Step 3: Cross multiply
   91.27x = 136.17 × 78.28
4. Step 4: Simplify right side
   91.27x = 10,659.39
5. Step 5: Solve for x
   x = 10,659.39/91.27
6. Step 6: Final answer
   x = 116.79