Finding the Third Proportional to 67.92 and 139.78

Step by Step Solution

1. Step 1: Write the proportion equation
   67.92 : 139.78 = 139.78 : x
2. Step 2: Convert to fraction form
   67.92/139.78 = 139.78/x
3. Step 3: Cross multiply
   67.92x = 139.78 × 139.78
4. Step 4: Simplify right side
   67.92x = 19,538.80
5. Step 5: Solve for x
   x = 19,538.80/67.92
6. Step 6: Final answer
   x = 287.67