$A$ bag contains $5$ red balls and some blue balls. If the probability of drawing a blue ball is double that of a red ball,determine the number of blue balls in the bag.

There are $40$ students in Class $X$ of a school,of whom $25$ are girls and $15$ are boys. The class teacher has to select one student as a class representative. She writes the name of each student on a separate card,the cards being identical. Then she puts cards in a bag and stirs them thoroughly. She then draws one card from the bag. What is the probability that the name written on the card is the name of $(i)$ a girl? $(ii)$ a boy?

$A$ bag contains lemon flavoured candies only. Malini takes out one candy without looking into the bag. What is the probability that she takes out
$(i)$ an orange flavoured candy?
$(ii)$ a lemon flavoured candy?

Savita and Hamida are friends. What is the probability that both will have $(i)$ different birthdays? $(ii)$ the same birthday? (ignoring a leap year).

Why is tossing a coin considered to be a fair way of deciding which team should get the ball at the beginning of a football game?

$A$ bag contains a red ball,a blue ball and a yellow ball,all the balls being of the same size. Kritika takes out a ball from the bag without looking into it. What is the probability that she takes out the
$(i)$ yellow ball?
$(ii)$ red ball?
$(iii)$ blue ball?