Finding the Fourth Proportional to 142.05, 212.77 and 90.72

Step by Step Solution

1. Step 1: Write the proportion equation
   142.05 : 212.77 = 90.72 : x
2. Step 2: Convert to fraction form
   142.05/212.77 = 90.72/x
3. Step 3: Cross multiply
   142.05x = 212.77 × 90.72
4. Step 4: Simplify right side
   142.05x = 19,300.98
5. Step 5: Solve for x
   x = 19,300.98/142.05
6. Step 6: Final answer
   x = 135.87