Finding the Third Proportional to 128.50 and 279.81

Step by Step Solution

1. Step 1: Write the proportion equation
   128.50 : 279.81 = 279.81 : x
2. Step 2: Convert to fraction form
   128.50/279.81 = 279.81/x
3. Step 3: Cross multiply
   128.50x = 279.81 × 279.81
4. Step 4: Simplify right side
   128.50x = 78,295.04
5. Step 5: Solve for x
   x = 78,295.04/128.50
6. Step 6: Final answer
   x = 609.30