Finding the Third Proportional to 190.78 and 390.56

Step by Step Solution

1. Step 1: Write the proportion equation
   190.78 : 390.56 = 390.56 : x
2. Step 2: Convert to fraction form
   190.78/390.56 = 390.56/x
3. Step 3: Cross multiply
   190.78x = 390.56 × 390.56
4. Step 4: Simplify right side
   190.78x = 152,539.07
5. Step 5: Solve for x
   x = 152,539.07/190.78
6. Step 6: Final answer
   x = 799.55