Finding the Fourth Proportional to 142.50, 212.88 and 90.72

Step by Step Solution

1. Step 1: Write the proportion equation
   142.50 : 212.88 = 90.72 : x
2. Step 2: Convert to fraction form
   142.50/212.88 = 90.72/x
3. Step 3: Cross multiply
   142.50x = 212.88 × 90.72
4. Step 4: Simplify right side
   142.50x = 19,312.47
5. Step 5: Solve for x
   x = 19,312.47/142.50
6. Step 6: Final answer
   x = 135.53