Finding the Third Proportional to 401,971.50 and 639,856.50

Step by Step Solution

1. Step 1: Write the proportion equation
   401,971.50 : 639,856.50 = 639,856.50 : x
2. Step 2: Convert to fraction form
   401,971.50/639,856.50 = 639,856.50/x
3. Step 3: Cross multiply
   401,971.50x = 639,856.50 × 639,856.50
4. Step 4: Simplify right side
   401,971.50x = 409,416,340,592.25
5. Step 5: Solve for x
   x = 409,416,340,592.25/401,971.50
6. Step 6: Final answer
   x = 1,018,520.82