Finding the Third Proportional to 321,420 and 691,213.50

Step by Step Solution

1. Step 1: Write the proportion equation
   321,420 : 691,213.50 = 691,213.50 : x
2. Step 2: Convert to fraction form
   321,420/691,213.50 = 691,213.50/x
3. Step 3: Cross multiply
   321,420x = 691,213.50 × 691,213.50
4. Step 4: Simplify right side
   321,420x = 477,776,102,582.25
5. Step 5: Solve for x
   x = 477,776,102,582.25/321,420
6. Step 6: Final answer
   x = 1,486,454.18