Finding the Third Proportional to 128.63 and 199.69

Step by Step Solution

1. Step 1: Write the proportion equation
   128.63 : 199.69 = 199.69 : x
2. Step 2: Convert to fraction form
   128.63/199.69 = 199.69/x
3. Step 3: Cross multiply
   128.63x = 199.69 × 199.69
4. Step 4: Simplify right side
   128.63x = 39,875.10
5. Step 5: Solve for x
   x = 39,875.10/128.63
6. Step 6: Final answer
   x = 310.01