### Instruction: Express eleven in base 2.### Response: To convert a number from base 10 to base 2, I need to divide it by 2 repeatedly and write down the remainders.
The remainders will form the digits of the base 2 number, starting from the rightmost one.
So, let me start by dividing 11 by 2.
I get 5 with a remainder of 1.
That means the rightmost digit of the base 2 number is 1.
Now I divide 5 by 2.
I get 2 with a remainder of 1.
That means the second rightmost digit is also 1.
Next, I divide 2 by 2.
I get 1 with a remainder of 0.
That means the third rightmost digit is 0.
Finally, I divide 1 by 2.
I get 0 with a remainder of 1.
That means the fourth rightmost digit is 1.
Since I have reached 0, I can stop dividing.
The base 2 number is formed by concatenating the remainders from right to left.
So, 11 in base 2 is 1011.