Finding the Fourth Proportional to 131.39, 196.89 and 77.21

Step by Step Solution

1. Step 1: Write the proportion equation
   131.39 : 196.89 = 77.21 : x
2. Step 2: Convert to fraction form
   131.39/196.89 = 77.21/x
3. Step 3: Cross multiply
   131.39x = 196.89 × 77.21
4. Step 4: Simplify right side
   131.39x = 15,200.89
5. Step 5: Solve for x
   x = 15,200.89/131.39
6. Step 6: Final answer
   x = 115.70