Finding the Third Proportional to 11.89 and 15.81

Step by Step Solution

1. Step 1: Write the proportion equation
   11.89 : 15.81 = 15.81 : x
2. Step 2: Convert to fraction form
   11.89/15.81 = 15.81/x
3. Step 3: Cross multiply
   11.89x = 15.81 × 15.81
4. Step 4: Simplify right side
   11.89x = 249.91
5. Step 5: Solve for x
   x = 249.91/11.89
6. Step 6: Final answer
   x = 21.01