Performing Arithmetic Operations

Linux(Performing Arithmetic Operations)
echo " ARITHMATIC OPERATIONS "
echo " ~~~~~~~~~~~~~~~~~~~~~ "
echo " Enter the two numbers "
read n1
read n2
echo " 1Addition "
echo " 2Subtraction "
echo " 3Multipication "
echo " 4Division "
echo " Enter your choice "
read ch
case $ch in
1) res=`expr $n1 + $n2`
echo " Added value is :" $res
;;
2) res=`expr $n1 - $n2`
echo " Subtraction value is :" $res
;;
3) res=`expr $n1 * $n2`
echo " Multipicaton value is:" $res
;;
4) res=`expr $n1 / $n2`
echo " Divided value is:" $res
;;
esac