Finding the Third Proportional to 100.78 and 205.78

Step by Step Solution

1. Step 1: Write the proportion equation
   100.78 : 205.78 = 205.78 : x
2. Step 2: Convert to fraction form
   100.78/205.78 = 205.78/x
3. Step 3: Cross multiply
   100.78x = 205.78 × 205.78
4. Step 4: Simplify right side
   100.78x = 42,345.92
5. Step 5: Solve for x
   x = 42,345.92/100.78
6. Step 6: Final answer
   x = 420.18