Finding the Third Proportional to 142.50 and 311.50

Step by Step Solution

1. Step 1: Write the proportion equation
   142.50 : 311.50 = 311.50 : x
2. Step 2: Convert to fraction form
   142.50/311.50 = 311.50/x
3. Step 3: Cross multiply
   142.50x = 311.50 × 311.50
4. Step 4: Simplify right side
   142.50x = 97,032.25
5. Step 5: Solve for x
   x = 97,032.25/142.50
6. Step 6: Final answer
   x = 680.93