Finding the Third Proportional to 76.78 and 136.69

Step by Step Solution

1. Step 1: Write the proportion equation
   76.78 : 136.69 = 136.69 : x
2. Step 2: Convert to fraction form
   76.78/136.69 = 136.69/x
3. Step 3: Cross multiply
   76.78x = 136.69 × 136.69
4. Step 4: Simplify right side
   76.78x = 18,683.47
5. Step 5: Solve for x
   x = 18,683.47/76.78
6. Step 6: Final answer
   x = 243.33