Finding the Third Proportional to 396.78 and 870.50

Step by Step Solution

1. Step 1: Write the proportion equation
   396.78 : 870.50 = 870.50 : x
2. Step 2: Convert to fraction form
   396.78/870.50 = 870.50/x
3. Step 3: Cross multiply
   396.78x = 870.50 × 870.50
4. Step 4: Simplify right side
   396.78x = 757,770.25
5. Step 5: Solve for x
   x = 757,770.25/396.78
6. Step 6: Final answer
   x = 1,909.79