Finding the Third Proportional to 128.75 and 279.50

Step by Step Solution

1. Step 1: Write the proportion equation
   128.75 : 279.50 = 279.50 : x
2. Step 2: Convert to fraction form
   128.75/279.50 = 279.50/x
3. Step 3: Cross multiply
   128.75x = 279.50 × 279.50
4. Step 4: Simplify right side
   128.75x = 78,120.25
5. Step 5: Solve for x
   x = 78,120.25/128.75
6. Step 6: Final answer
   x = 606.76