Finding the Third Proportional to 111.75 and 128.50

Step by Step Solution

1. Step 1: Write the proportion equation
   111.75 : 128.50 = 128.50 : x
2. Step 2: Convert to fraction form
   111.75/128.50 = 128.50/x
3. Step 3: Cross multiply
   111.75x = 128.50 × 128.50
4. Step 4: Simplify right side
   111.75x = 16,512.25
5. Step 5: Solve for x
   x = 16,512.25/111.75
6. Step 6: Final answer
   x = 147.76