Finding the Third Proportional to 12,870 and 21,276

Step by Step Solution

1. Step 1: Write the proportion equation
   12,870 : 21,276 = 21,276 : x
2. Step 2: Convert to fraction form
   12,870/21,276 = 21,276/x
3. Step 3: Cross multiply
   12,870x = 21,276 × 21,276
4. Step 4: Simplify right side
   12,870x = 452,668,176
5. Step 5: Solve for x
   x = 452,668,176/12,870
6. Step 6: Final answer
   x = 35,172.35