Finding the Third Proportional to 39,699 and 78,390

Step by Step Solution

1. Step 1: Write the proportion equation
   39,699 : 78,390 = 78,390 : x
2. Step 2: Convert to fraction form
   39,699/78,390 = 78,390/x
3. Step 3: Cross multiply
   39,699x = 78,390 × 78,390
4. Step 4: Simplify right side
   39,699x = 6,144,992,100
5. Step 5: Solve for x
   x = 6,144,992,100/39,699
6. Step 6: Final answer
   x = 154,789.59