Finding the Third Proportional to 136.88 and 256.31

Step by Step Solution

1. Step 1: Write the proportion equation
   136.88 : 256.31 = 256.31 : x
2. Step 2: Convert to fraction form
   136.88/256.31 = 256.31/x
3. Step 3: Cross multiply
   136.88x = 256.31 × 256.31
4. Step 4: Simplify right side
   136.88x = 65,696.10
5. Step 5: Solve for x
   x = 65,696.10/136.88
6. Step 6: Final answer
   x = 479.97