Finding the Fourth Proportional to 142.15, 196.12 and 86.91

Step by Step Solution

1. Step 1: Write the proportion equation
   142.15 : 196.12 = 86.91 : x
2. Step 2: Convert to fraction form
   142.15/196.12 = 86.91/x
3. Step 3: Cross multiply
   142.15x = 196.12 × 86.91
4. Step 4: Simplify right side
   142.15x = 17,044.57
5. Step 5: Solve for x
   x = 17,044.57/142.15
6. Step 6: Final answer
   x = 119.91