Finding the Fourth Proportional to 91.43, 136.81 and 78.74

Step by Step Solution

1. Step 1: Write the proportion equation
   91.43 : 136.81 = 78.74 : x
2. Step 2: Convert to fraction form
   91.43/136.81 = 78.74/x
3. Step 3: Cross multiply
   91.43x = 136.81 × 78.74
4. Step 4: Simplify right side
   91.43x = 10,771.34
5. Step 5: Solve for x
   x = 10,771.34/91.43
6. Step 6: Final answer
   x = 117.82