Finding the Third Proportional to 420,381 and 640,291.50

Step by Step Solution

1. Step 1: Write the proportion equation
   420,381 : 640,291.50 = 640,291.50 : x
2. Step 2: Convert to fraction form
   420,381/640,291.50 = 640,291.50/x
3. Step 3: Cross multiply
   420,381x = 640,291.50 × 640,291.50
4. Step 4: Simplify right side
   420,381x = 409,973,204,972.25
5. Step 5: Solve for x
   x = 409,973,204,972.25/420,381
6. Step 6: Final answer
   x = 975,241.99