# The studens of a class take a test having 10 questions of true or false objective type questions. No two students answer are same. None of the students has got all the answers correct. How many students are there in the class.

$\begin{array}{1 1} 2^{10}-1 \\ 2^9 -1 \\ 2^9 \\ 2^{10} \end{array}$

There are $2^{10}$ different answers (answer sheets) for the test
This includes one answer sheet in which all answers are correct .
But it is given that no one has given all the answers correct.
$\therefore$ The no. of students = $2^{10}-1$