A bookcase contains 2 statistics books and 5 biology books. If 2 books are chosen at random, the chance that both are statistics books is
A) $\frac { 10 } { 11 }$
B) $\frac { 1 } { 21 }$
C) $\frac { 10 } { 21 }$
D) $\frac { 1 } { 11 }$

Question

A bookcase contains 2 statistics books and 5 biology books. If 2 books are chosen at random, the chance that both are statistics books is 
A) $\frac { 10 } { 11 }$
B) $\frac { 1 } { 21 }$
C) $\frac { 10 } { 21 }$
D) $\frac { 1 } { 11 }$

Quizplus · Accepted Answer

The probability of choosing both statistics books is calculated by dividing the number of ways to choose 2 statistics books by the total number of ways to choose any 2 books from the 7 available. The number of ways to choose 2 statistics books is $\binom{2}{2} = 1$, and the total number of ways to choose any 2 books from 7 is $\binom{7}{2} = 21$. Therefore, the probability is $\frac{1}{21}$.

A Bookcase Contains 2 Statistics Books and 5 Biology Books 1011\frac { 10 } { 11 }1110​

A Bookcase Contains 2 Statistics Books and 5 Biology Books $\frac { 10 } { 11 }$