Finding the Third Proportional to 12,780 and 15,516

Step by Step Solution

1. Step 1: Write the proportion equation
   12,780 : 15,516 = 15,516 : x
2. Step 2: Convert to fraction form
   12,780/15,516 = 15,516/x
3. Step 3: Cross multiply
   12,780x = 15,516 × 15,516
4. Step 4: Simplify right side
   12,780x = 240,746,256
5. Step 5: Solve for x
   x = 240,746,256/12,780
6. Step 6: Final answer
   x = 18,837.74