Finding the Third Proportional to 15,321 and 21,680

Step by Step Solution

1. Step 1: Write the proportion equation
   15,321 : 21,680 = 21,680 : x
2. Step 2: Convert to fraction form
   15,321/21,680 = 21,680/x
3. Step 3: Cross multiply
   15,321x = 21,680 × 21,680
4. Step 4: Simplify right side
   15,321x = 470,022,400
5. Step 5: Solve for x
   x = 470,022,400/15,321
6. Step 6: Final answer
   x = 30,678.31