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Form 3 Probability Video Questions and Answers

Form 3 Probability Video Questions and Answers.
Revise online using video questions and answers on probability.

Lessons (30)

• 1.    A contractor applies for two contracts: A-building a school workshop and B-building a school library. The probability of getting contract A is 0.6.The probability of getting contract B depends on whether or not A is obtained and 0.7 if A is obtained but only 0.4 if A is not obtained. What is the probability of getting at least one contract?
  3m 10s

• 2.    A bag contain 10 balls of which 3 are red,5 are white and 2 are green .Another bag contains 12 balls of which are 4 are red,3 are white and 5 are green. A bag is chosen at random and then a ball chosen at random from the bag .Find the probability that the ball so chosen is red.
  2m 16s

• 3.    At a factory 120 candidates have to be interviewed:48 for carpentry,32 for masonry and 40 for plumbing.Past experience indicates that 80% would pass carpentry,45% would pass masonry and 60% would pass plumbing. (a) A candidate is picked at random.Find the probability that (i) he is to be interviewed for the carpentry. (ii) he is to be interviewed for masonry and would pass. (iii) he would pass the
  6m 6s

• 4.    There are two boxes labelled A and B on a table. Box A contains 5 red balls and 3 white balls,while box B contains 2 red balls and 6 white balls. A box is chosen at random and two balls are drawn from it,one after the other without replacement. Find probability that the two balls chosen are of different colours.
  4m 15s

• 5.    In a shooting practice three soldiers A,B and C aim at a target. The probabilities of A,B and C hitting the target are #1/3, 1/4 and 1/2# respectively. The three soldiers shot at the target only once; one after the other. What is the probability that the target was hit only once?
  3m 13s

• 6.    The probability that Kamau will be selected for his school’s basketball team is #1/4#. If he is selected for the basketball team, then the probability that he will be selected for a football is #1/3#. If he is not selected for basketball then the probability that he is selected for football is #4/5# . What is the probability that Kamau is selected for at least one of the two games?
  2m 0s

• 7.    Chicks on Onyango’s farm were noted to have either brown or black feathers. Of those with black feathers #2/3# were female while #2/5# of those with brown feathers were male. Otieno bought two chicks from Onyango.One had black tail feathers while the other had brown. Find the probability that Otieno’s chicks were not to the same gender.
  2m 3s

• 8.    The probability that a man wins a game is #3/4#. He plays the game until he wins. Determine the probability that he wins in the fifth round.
  1m 27s

• 9.    Two baskets A and B each contains a mixture of oranges and lemons. Basket A contains 26 oranges and 13 lemons. Basket B contains 18 oranges and 15 lemons. A child selected a basket random and picked at random a fruit from it. Determine the probability that the fruit picked was an orange.
  2m 3s

• 10.    The probabilities that a husband and a wife will be alive 25 years from now are 0.7 and 0.9 respectively. Find the probability that in 25 years time, (a) Both will be alive. (b) Neither will be alive (c) One will be alive (d) At least one will be alive
  3m 44s

• 11.    A bag contain blue, green and red pens of the same type in the ratio 8:2:5 respectively. A pen is picked at random without replacement, and its colour noted. (a) Determine the probability that the first pen picked is (i) Blue (ii) Either green or red (b) Using a tree diagram determine the probability that (i)the first two pens picked are both green (ii)only one of the first two pens picked is red.
  1m 54s

• 12.    During inter-school competitions, football and volleyball teams from Mokagu High School took part. The probability that their football and volleyball teams would win were #3/8# and #4/7# respectively. Find the probability that: (a)both their football and volleyball teams won. (b) at least one of their teams won.
  2m 39s

• 13.    The water supply in a town depends entirely on two water pumps A and B. The probability of pump A failing is 0.1 and the probability of pump B failing is 0.2. Calculate the probability that (a)both pump are working (b)there are no water in the town (c)only one pump is working (d)there is some water in the town.
  4m 24s

• 14.    In a livestock research station a new drug for a certain fowl disease is being tried. A sample of 36 fowls was diagnosed to have the disease. Twenty (20) fowls were treated with the drug and the rest were not. (a) Calculate the probability that fowl picked at random is (i)treated with the drug . (ii)not treated with the drug. (b) If a fowl is treated, the probability of dying is# 1 /10#
  4m 6s

• 15.    A science club is made up of 5 boys and 7 girls. The club has 3 officials. Using a tree diagram or otherwise find the probability that (a)the club officials are all boys (b)two of the officials are girls
  3m 15s

• 16.    Two baskets A and B each contains a mixture of oranges and limes,all of the same size. Basket A contains 26 oranges and 13 limes. Basket B contains 18 oranges and 15 limes. A child selected a basket at random and picked a fruit at random from it. (a) Illustrate this information by a probability tree diagram (b) Find the probability that the fruit picked was an orange.
  3m 26s

• 17.    In a form one class there are 22 girls and 18 boys. The probability of a girl completing the secondary educating course is #3/5# whereas that of a boy is #2/3#. (a) A student is picked at random from the class. Find the possibility that, (i)the student picked is a boy and will complete the course. (ii)the student picked will complete the course. (b) Two students are picked at random. Find the
  2m 58s

• 18.    Three representatives are to be selected randomly from a group of 7 girls and 8 boys. Calculate the probability of selecting two girls and one boy.
  2m 35s

• 19.    A poultry farmer vaccinated 540 of his 720 chickens against a disease. Two months later 5% of the vaccinated and 80% of the unvaccinated chickens contracted the disease. Calculate the probability that a chicken chosen at random contracted the disease.
  2m 23s

• 20.    An unbiased coin with two faces ,head (H) and tail(T) is tossed three times. List all the possible outcomes. Hence determine the probability of getting (a)at least two heads (b)only one tail.
  2m 17s

• 21.    There are three cars A,B and C in a race.A is twice as likely to win as B while B is twice as likely to win as C. Find the probability that (a) A wins the race (b) Either B or C wins the race.
  1m 46s

• 22.    In the year 2003,the population of a certain district was 1.8 million. Thirty percent of the population was in the age group 15-40 years. In the same year, 120,000 people in the district visited the voluntary Counselling and Testing (VCT) centre for an HIV test. If a person was selected at random from the district in that year,find the probability that the person visited a VCT centre and was in
  1m 59s

• 23.    Two teachers are chosen randomly from a staff consisting of 3 women and 2 men to attend a HIV/AIDS seminar. Calculate the probability that the two teachers chosen are (a)of the same sex. (b)of opposite sex.
  2m 13s

• 24.    Two bags A and B contains identical balls except for the colours. Bag A contain 4 red balls 3 and 2 yellow balls. Bag B contains 2 red balls and 3 yellow balls. (a) If a ball is drawn at random from each bag, find the probability that both balls are of the same colour. (b) If two balls are drawn at random from each bag, one ball one ball at a time without replacement, find the probability that
  4m 38s

• 25.    A student at a certain college has 60% chances of passing an examination at the first attempt. Each time a student fails and repeats the examination,his chances of passing are increased by 15%. Calculate the probability that the student in the college passes an examination at the second or at the third attempt.
  4m 30s

• 26.    On a certain day,the probability that it rains is#1/7#. When it rains the probability that Oguta carries an umbrella is #2/5#. When it does not rain the probability that Oguta carries an umbrella is #1/6#. Find the probability that Oguta carried an umbrella that day.
  1m 43s

• 27.    The ages in years of 5 boys are 7,8,9,10 and 11while those of 5 girls are 4,5,6,7 and 8. A boy and a girl are picked at random and the sum of their ages are recorded. (a) Draw a probability space to show all the possible outcome. (b) Find the probability that the sum of their ages is at least 17 years.
  4m 46s

• 28.    In an nomination for a committee,two people were to be selected at random from a group of 3 men and women. Find the probability that a man and a woman were selected.
  1m 23s

• 29.    In a certain firm there are 6 men 4 women employees. Two employees are chosen at random to attend a seminar. Determine the probability that a man and a woman are chosen.
  1m 34s

• 30.    A bag contain 6 red counters and 4 blue counters. Two counters are picked from the bag at random, without replacement. (a) Represent the events using a tree diagram. (b) Find the probability that the two counters are of the same colour.
  2m 29s