Finding the Third Proportional to 78,740 and 172,840

Step by Step Solution

1. Step 1: Write the proportion equation
   78,740 : 172,840 = 172,840 : x
2. Step 2: Convert to fraction form
   78,740/172,840 = 172,840/x
3. Step 3: Cross multiply
   78,740x = 172,840 × 172,840
4. Step 4: Simplify right side
   78,740x = 29,873,665,600
5. Step 5: Solve for x
   x = 29,873,665,600/78,740
6. Step 6: Final answer
   x = 379,396.31