Finding the Third Proportional to 12,840 and 19,708.50

Step by Step Solution

1. Step 1: Write the proportion equation
   12,840 : 19,708.50 = 19,708.50 : x
2. Step 2: Convert to fraction form
   12,840/19,708.50 = 19,708.50/x
3. Step 3: Cross multiply
   12,840x = 19,708.50 × 19,708.50
4. Step 4: Simplify right side
   12,840x = 388,424,972.25
5. Step 5: Solve for x
   x = 388,424,972.25/12,840
6. Step 6: Final answer
   x = 30,251.17