Finding the Third Proportional to 64.78 and 139.69

Step by Step Solution

1. Step 1: Write the proportion equation
   64.78 : 139.69 = 139.69 : x
2. Step 2: Convert to fraction form
   64.78/139.69 = 139.69/x
3. Step 3: Cross multiply
   64.78x = 139.69 × 139.69
4. Step 4: Simplify right side
   64.78x = 19,512.60
5. Step 5: Solve for x
   x = 19,512.60/64.78
6. Step 6: Final answer
   x = 301.21