Finding the Fourth Proportional to 91.58, 136.71 and 77.81

Step by Step Solution

1. Step 1: Write the proportion equation
   91.58 : 136.71 = 77.81 : x
2. Step 2: Convert to fraction form
   91.58/136.71 = 77.81/x
3. Step 3: Cross multiply
   91.58x = 136.71 × 77.81
4. Step 4: Simplify right side
   91.58x = 10,636.72
5. Step 5: Solve for x
   x = 10,636.72/91.58
6. Step 6: Final answer
   x = 116.15