Finding the Third Proportional to 345.78 and 518.72

Step by Step Solution

1. Step 1: Write the proportion equation
   345.78 : 518.72 = 518.72 : x
2. Step 2: Convert to fraction form
   345.78/518.72 = 518.72/x
3. Step 3: Cross multiply
   345.78x = 518.72 × 518.72
4. Step 4: Simplify right side
   345.78x = 269,069.14
5. Step 5: Solve for x
   x = 269,069.14/345.78
6. Step 6: Final answer
   x = 778.15