Use of Probability

Let us look at some more occasions where probability may be useful. We know that in sports some countries are strong and others are not so strong. We also know that when two players are playing it is not that they win equal times. The probability of winning of the player or team that wins more often is more than the probability of the other player or team. We also discuss and keep track of birthdays. Sometimes it happens that people we know have the same birthdays. Can we find out whether this is a common event or would it only happen occasionally. Classical probability helps us do this.

5. Two players, Sangeeta and Reshma, play a tennis match. It is known that the probability of Sangeeta winning the match is 0.62. What is the probability of Reshma winning the match?

Example 6

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

Example 7

7. 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?

Note : We can also determine P(Boy), by taking P(Boy) = 1 – P(not Boy) = 1 – P(Girl) = 1- 58 =

Example 8