Finding the Third Proportional to 39,978 and 86,478

Step by Step Solution

1. Step 1: Write the proportion equation
   39,978 : 86,478 = 86,478 : x
2. Step 2: Convert to fraction form
   39,978/86,478 = 86,478/x
3. Step 3: Cross multiply
   39,978x = 86,478 × 86,478
4. Step 4: Simplify right side
   39,978x = 7,478,444,484
5. Step 5: Solve for x
   x = 7,478,444,484/39,978
6. Step 6: Final answer
   x = 187,064.00