Finding the Third Proportional to 315.78 and 683.69

Step by Step Solution

1. Step 1: Write the proportion equation
   315.78 : 683.69 = 683.69 : x
2. Step 2: Convert to fraction form
   315.78/683.69 = 683.69/x
3. Step 3: Cross multiply
   315.78x = 683.69 × 683.69
4. Step 4: Simplify right side
   315.78x = 467,428.60
5. Step 5: Solve for x
   x = 467,428.60/315.78
6. Step 6: Final answer
   x = 1,480.23