Finding the Third Proportional to 688.50 and 799.50

Step by Step Solution

1. Step 1: Write the proportion equation
   688.50 : 799.50 = 799.50 : x
2. Step 2: Convert to fraction form
   688.50/799.50 = 799.50/x
3. Step 3: Cross multiply
   688.50x = 799.50 × 799.50
4. Step 4: Simplify right side
   688.50x = 639,200.25
5. Step 5: Solve for x
   x = 639,200.25/688.50
6. Step 6: Final answer
   x = 928.40