A group consists of $4$ girls and $7$ boys. In how many ways can a team of $5$ members be selected if the team has at least one boy and one girl ?
since, at least one boy and one girl are to be there in every team. Therefore, the team can consist of
$(a)$ $1$ boy and $4$ girls
$(b)$ $2$ boys and $3$ girls
$(c)$ $3$ boys and $2$ girls
$(d)$ $4$ boys and $1$ girl.
$1$ boy and $4$ girls can be selected in $^{7} C _{1} \times^{4} C _{4}$ ways.
$2$ boys and $3$ girls can be selected in $^{7} C _{2} \times^{4} C _{3}$ ways.
$3$ boys and $2$ girls can be selected in $^{7} C _{3} \times^{4} C _{2}$ ways.
$4$ boys and $1$ girl can be selected in $^{7} C _{4} \times^{4} C _{1}$ ways.
Therefore, the required number of ways
$=\,^{7} C _{1} \times^{4} C _{4}+^{7} C _{2} \times^{4} C _{3}+^{7} C _{3} \times^{4} C _{2}+^{7} C _{4} \times^{4} C _{1}$
$=7+84+210+140=441$
Out of $6$ books, in how many ways can a set of one or more books be chosen
Determine $n$ if
$^{2 n} C_{3}:^{n} C_{3}=11: 1$
Suppose Anil's mother wants to give $5$ whole fruits to Anil from a basket of $7$ red apples, $5$ white apples and $8$ oranges. If in the selected $5$ fruits, at least $2$ orange, at least one red apple and at least one white apple must be given, then the number of ways, Anil's mother can offer $5$ fruits to Anil is $........$
Statement$-1:$ The number of ways of distributing $10$ identical balls in $4$ distinct boxes such that no box is empty is $^9C_3 .$
Statement$-2:$ The number of ways of choosing any $3$ places from $9$ different places is $^9C_3 $.
Find the number of ways in which two Americans, two British, One Chinese, One Dutch and one Egyptian can sit on a round table so that person of the same nationality are separated?