Finding the Third Proportional to 121.50 and 131.50

Step by Step Solution

1. Step 1: Write the proportion equation
   121.50 : 131.50 = 131.50 : x
2. Step 2: Convert to fraction form
   121.50/131.50 = 131.50/x
3. Step 3: Cross multiply
   121.50x = 131.50 × 131.50
4. Step 4: Simplify right side
   121.50x = 17,292.25
5. Step 5: Solve for x
   x = 17,292.25/121.50
6. Step 6: Final answer
   x = 142.32