Finding the Third Proportional to 30,990 and 67,129.50

Step by Step Solution

1. Step 1: Write the proportion equation
   30,990 : 67,129.50 = 67,129.50 : x
2. Step 2: Convert to fraction form
   30,990/67,129.50 = 67,129.50/x
3. Step 3: Cross multiply
   30,990x = 67,129.50 × 67,129.50
4. Step 4: Simplify right side
   30,990x = 4,506,369,770.25
5. Step 5: Solve for x
   x = 4,506,369,770.25/30,990
6. Step 6: Final answer
   x = 145,413.67