Finding the Third Proportional to 399 and 1,061.50

Step by Step Solution

1. Step 1: Write the proportion equation
   399 : 1,061.50 = 1,061.50 : x
2. Step 2: Convert to fraction form
   399/1,061.50 = 1,061.50/x
3. Step 3: Cross multiply
   399x = 1,061.50 × 1,061.50
4. Step 4: Simplify right side
   399x = 1,126,782.25
5. Step 5: Solve for x
   x = 1,126,782.25/399
6. Step 6: Final answer
   x = 2,824.02