Whenever we're unsure about the outcome of an event, we can talk about the probabilities of certain outcomes — how likely they are. OR Many events can't be predicted with total certainty. The best we can say is how likely they are to happen, using the idea of probability.
Probability of an Event = Number of ways it can happen / Total number of outcomes
Let us understand, What is equally likely Events or outcomes? When tossing a coin, There are two possible outcomes of an experiment:
Head (H) or Tail (T)
Probability of getting a Head is 1/2
Probability of getting a Tail is 1/2
We have seen in the experiment of tossing a coin that each of the outcome has the same chance of occurring.
When each of the outcome of the experiment has the same chance of occurring then we can say , the outcomes of the experiment are equally likely.
Q. Numbers 1 to 10 are written on ten separate slips ( one number on one slip) kept in a box and mixed well. One slip is chosen from the box without looking into it. (a) What is the probability of getting a number 6 ? (b) What is the probability of getting a number greater than 6 ?Ans: (a) Total No of slips = 10 Number of slips on which 6 is written = 1 Probability = Number of slips on which 6 is written / Total No of slips = 1/ 10 (b) Numbers greater than 6 are 7, 8, 9, ... read more
Q. A book contains 90 pages which are numbered from 1 to 90. If one page is opened at random from the book, find the probability that it will be-- (i) a two digit number (ii) a perfect square number (iii) a number divisible by 5.Ans: As book contains 90 pages which are numbered from 1 to 90 So total numbers of outcome is n(S) = 90 (i) Let E be the event of a two digit number Total Single digit number from 1 to 9... read more
Q. A bag contains 5 red marbles, 8 white marbles and 4 green marbles. One marble is taken out of the bag at random. What is the probability that marble taken out will be - (i) red (ii) white (iii) not green.Ans: Total number of marbles = 5 + 8 + 4 = 17 So total numbers of outcome is n(S) = 17 (i) Let E be the event of taken out marble will be red Total number of red marbles is... read more
Q. Dan either walks or cycles to school.The probability that he cycles to school is 1/5. There are 200 days in a school year. Work out the expected number of days that Dan cycles to school in a school year.Ans: As Dan either walks or cycles to school. The probability that he cycles to school is 1/5 Total number of days in school year = 200 Expected number of days that Dan cycles to school in a school ye... read more