Exam-Style Problems

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June 2023 p53 q5
2653

Jasmine throws two ordinary fair 6-sided dice at the same time and notes the numbers on the uppermost faces. The events A and B are defined as follows.

A: The sum of the two numbers is less than 6.

B: The difference between the two numbers is at most 2.

Determine whether or not the events A and B are independent.

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June 2019 p61 q3
2654

A fair six-sided die is thrown twice and the scores are noted. Event X is defined as ‘The total of the two scores is 4’. Event Y is defined as ‘The first score is 2 or 5’. Are events X and Y independent? Justify your answer.

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Nov 2018 p61 q7
2655

In a group of students, the numbers of boys and girls studying Art, Music and Drama are given in the following table. Each of these 160 students is studying exactly one of these subjects.

ArtMusicDrama
Boys244032
Girls151237
  1. Find the probability that a randomly chosen student is studying Music.
  2. Determine whether the events ‘a randomly chosen student is a boy’ and ‘a randomly chosen student is studying Music’ are independent, justifying your answer.
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June 2018 p62 q2
2656

In a group of students, \(\frac{3}{4}\) are male. The proportion of male students who like their curry hot is \(\frac{3}{5}\) and the proportion of female students who like their curry hot is \(\frac{4}{5}\). One student is chosen at random.

  1. Find the probability that the student chosen is either female, or likes their curry hot, or is both female and likes their curry hot.
  2. Showing your working, determine whether the events ‘the student chosen is male’ and ‘the student chosen likes their curry hot’ are independent.
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Problem 2657
2657

Last Saturday, Sarah recorded the colour and type of 160 cars in a car park. All the cars that were not red or silver in colour were grouped together as 'other'. Her results are shown in the following table.

Colour of carSaloonHatchbackEstate
Red204012
Silver142610
Other6248
  1. Find the probability that a randomly chosen car in the car park is a silver estate car. [1]
  2. Find the probability that a randomly chosen car in the car park is a hatchback car. [1]
  3. Find the probability that a randomly chosen car in the car park is red, given that it is a hatchback car. [2]
  4. One of the cars in the car park is chosen at random. Determine whether the events 'the car is a hatchback car' and 'the car is red' are independent, justifying your answer. [2]
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June 2017 p61 q2
2658

Ashfaq throws two fair dice and notes the numbers obtained. R is the event 'The product of the two numbers is 12'. T is the event 'One of the numbers is odd and one of the numbers is even'. By finding appropriate probabilities, determine whether events R and T are independent.

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Nov 2016 p63 q4
2659

For a group of 250 cars the numbers, classified by colour and country of manufacture, are shown in the table.

GermanyJapanKorea
Silver402634
White322226
Red281230

One car is selected at random from this group. Find the probability that the selected car is

  1. a red or silver car manufactured in Korea,
  2. not manufactured in Japan.

X is the event that the selected car is white. Y is the event that the selected car is manufactured in Germany.

(iii) By using appropriate probabilities, determine whether events X and Y are independent.

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June 2016 p63 q1
2660

In a group of 30 adults, 25 are right-handed and 8 wear spectacles. The number who are right-handed and do not wear spectacles is 19.

(i) Copy and complete the following table to show the number of adults in each category.

Wears spectaclesDoes not wear spectaclesTotal
Right-handed
Not right-handed
Total30

An adult is chosen at random from the group. Event X is ‘the adult chosen is right-handed’; event Y is ‘the adult chosen wears spectacles’.

(ii) Determine whether X and Y are independent events, justifying your answer.

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Feb/Mar 2016 p62 q3
2661

A fair eight-sided die has faces marked 1, 2, 3, 4, 5, 6, 7, 8. The score when the die is thrown is the number on the face the die lands on. The die is thrown twice.

  • Event R is ‘one of the scores is exactly 3 greater than the other score’.
  • Event S is ‘the product of the scores is more than 19’.
  1. Find the probability of R. [2]
  2. Find the probability of S. [2]
  3. Determine whether events R and S are independent. Justify your answer. [3]
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Nov 2015 p63 q3
2662

Ellie throws two fair tetrahedral dice, each with faces numbered 1, 2, 3, and 4. She notes the numbers on the faces that the dice land on. Event S is 'the sum of the two numbers is 4'. Event T is 'the product of the two numbers is an odd number'.

  1. Determine whether events S and T are independent, showing your working.
  2. Are events S and T exclusive? Justify your answer.
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June 2015 p61 q3
2663

Jason throws two fair dice, each with faces numbered 1 to 6. Event A is ‘one of the numbers obtained is divisible by 3 and the other number is not divisible by 3’. Event B is ‘the product of the two numbers obtained is even’.

  1. Determine whether events A and B are independent, showing your working. [5]
  2. Are events A and B mutually exclusive? Justify your answer. [1]
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Feb/Mar 2023 p52 q5
2664

Marco has four boxes labelled K, L, M and N. He places them in a straight line in the order K, L, M, N with K on the left. Marco also has four coloured marbles: one is red, one is green, one is white and one is yellow. He places a single marble in each box, at random. Events A and B are defined as follows.

A: The white marble is in either box L or box M.

B: The red marble is to the left of both the green marble and the yellow marble.

Determine whether or not events A and B are independent.

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Nov 2013 p62 q7
2665

Rory has 10 cards. Four of the cards have a 3 printed on them and six of the cards have a 4 printed on them. He takes three cards at random, without replacement, and adds up the numbers on the cards. Event \(R\) is 'the sum of the numbers on the three cards is 11'. Event \(S\) is 'the number on the first card taken is a 3'.

(iii) Determine whether events \(R\) and \(S\) are independent. Justify your answer.

(iv) Determine whether events \(R\) and \(S\) are exclusive. Justify your answer.

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June 2013 p63 q1
2666

Q is the event ‘Nicola throws two fair dice and gets a total of 5’. S is the event ‘Nicola throws two fair dice and gets one low score (1, 2 or 3) and one high score (4, 5 or 6)’. Are events Q and S independent? Justify your answer.

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Nov 2012 p63 q3
2667

Ronnie obtained data about the gross domestic product (GDP) and the birth rate for 170 countries. He classified each GDP and each birth rate as either ‘low’, ‘medium’ or ‘high’. The table shows the number of countries in each category.

Birth rate
GDPLowMediumHigh
Low3545
Medium204212
High3580

One of these countries is chosen at random.

  1. Find the probability that the country chosen has a medium GDP. [1]
  2. Find the probability that the country chosen has a low birth rate, given that it does not have a medium GDP. [2]
  3. State with a reason whether or not the events ‘the country chosen has a high GDP’ and ‘the country chosen has a high birth rate’ are exclusive. [2]

One country is chosen at random from those countries which have a medium GDP and then a different country is chosen at random from those which have a medium birth rate.

  1. Find the probability that both countries chosen have a medium GDP and a medium birth rate. [3]
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June 2012 p63 q5
2668

Suzanne has 20 pairs of shoes, some of which have designer labels. She has 6 pairs of high-heeled shoes, of which 2 pairs have designer labels. She has 4 pairs of low-heeled shoes, of which 1 pair has designer labels. The rest of her shoes are pairs of sports shoes. Suzanne has 8 pairs of shoes with designer labels in total.

(i) Copy and complete the table below to show the number of pairs in each category.

Designer labelsNo designer labelsTotal
High-heeled shoes6
Low-heeled shoes4
Sports shoes
Total20

Suzanne chooses 1 pair of shoes at random to wear.

(ii) Find the probability that she wears the pair of low-heeled shoes with designer labels.

(iii) Find the probability that she wears a pair of sports shoes.

(iv) Find the probability that she wears a pair of high-heeled shoes, given that she wears a pair of shoes with designer labels.

(v) State with a reason whether the events ‘Suzanne wears a pair of shoes with designer labels’ and ‘Suzanne wears a pair of sports shoes’ are independent.

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Nov 2011 p63 q2
2669

In a group of 30 teenagers, 13 of the 18 males watch 'Kops are Kids' on television and 3 of the 12 females watch 'Kops are Kids'.

(i) Find the probability that a person chosen at random from the group is either female or watches 'Kops are Kids' or both.

(ii) Showing your working, determine whether the events 'the person chosen is male' and 'the person chosen watches Kops are Kids' are independent or not.

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Nov 2011 p61 q7
2670

Bag A contains 4 balls numbered 2, 4, 5, 8. Bag B contains 5 balls numbered 1, 3, 6, 8, 8. Bag C contains 7 balls numbered 2, 7, 8, 8, 8, 8, 9. One ball is selected at random from each bag.

  1. Find the probability that exactly two of the selected balls have the same number.
  2. Given that exactly two of the selected balls have the same number, find the probability that they are both numbered 2.
  3. Event X is ‘exactly two of the selected balls have the same number’. Event Y is ‘the ball selected from bag A has number 2’. Showing your working, determine whether events X and Y are independent or not.
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June 2011 p63 q4
2671

Tim throws a fair die twice and notes the number on each throw.

(i) Tim calculates his final score as follows. If the number on the second throw is a 5 he multiplies the two numbers together, and if the number on the second throw is not a 5 he adds the two numbers together. Find the probability that his final score is

(a) 12,

(b) 5.

(ii) Events A, B, C are defined as follows.

A: the number on the second throw is 5

B: the sum of the numbers is 6

C: the product of the numbers is even

By calculation find which pairs, if any, of the events A, B and C are independent.

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June 2010 p62 q5
2672

Two fair twelve-sided dice with sides marked 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 are thrown, and the numbers on the sides which land face down are noted. Events \(Q\) and \(R\) are defined as follows.

\(Q\): the product of the two numbers is 24.
\(R\): both of the numbers are greater than 8.

  1. Find \(P(Q)\). [2]
  2. Find \(P(R)\). [2]
  3. Are events \(Q\) and \(R\) exclusive? Justify your answer. [2]
  4. Are events \(Q\) and \(R\) independent? Justify your answer. [2]
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Nov 2006 p6 q4
2673

Two fair dice are thrown.

  1. Event A is ‘the scores differ by 3 or more’. Find the probability of event A.
  2. Event B is ‘the product of the scores is greater than 8’. Find the probability of event B.
  3. State with a reason whether events A and B are mutually exclusive.
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June 2005 p6 q5
2674

Data about employment for males and females in a small rural area are shown in the table.

UnemployedEmployed
Male206412
Female358305

A person from this area is chosen at random. Let \(M\) be the event that the person is male and let \(E\) be the event that the person is employed.

  1. Find \(P(M)\).
  2. Find \(P(M \text{ and } E)\).
  3. Are \(M\) and \(E\) independent events? Justify your answer.
  4. Given that the person chosen is unemployed, find the probability that the person is female.
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Nov 2022 p51 q5
2675

A game is played with an ordinary fair 6-sided die. A player throws the die once. If the result is 2, 3, 4, or 5, that result is the player's score and the player does not throw the die again. If the result is 1 or 6, the player throws the die a second time and the player's score is the sum of the two numbers from the two throws.

(a) Draw a fully labelled tree diagram to represent this information.

Events A and B are defined as follows.

A: the player's score is 5, 6, 7, 8 or 9

B: the player has two throws

(b) Show that P(A) = \(\frac{1}{3}\).

(c) Determine whether or not events A and B are independent.

(d) Find P(B | A').

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June 2002 p6 q1
2676

Events A and B are such that \(P(A) = 0.3\), \(P(B) = 0.8\) and \(P(A \text{ and } B) = 0.4\). State, giving a reason in each case, whether events A and B are

  1. independent,
  2. mutually exclusive.
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Nov 2021 p52 q1
2677

Each of the 180 students at a college plays exactly one of the piano, the guitar, and the drums. The numbers of male and female students who play the piano, the guitar, and the drums are given in the following table.

PianoGuitarDrums
Male254411
Female423820

A student at the college is chosen at random.

  1. (a) Find the probability that the student plays the guitar.
  2. (c) Determine whether the events ‘the student plays the guitar’ and ‘the student is female’ are independent, justifying your answer.
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Feb/Mar 2021 p52 q7
2678

There are 400 students at a school in a certain country. Each student was asked whether they preferred swimming, cycling or running and the results are given in the following table.

SwimmingCyclingRunning
Female1045066
Male315792

A student is chosen at random.

  1. Find the probability that the student prefers swimming. [1]
  2. Determine whether the events ‘the student is male’ and ‘the student prefers swimming’ are independent, justifying your answer. [2]
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Nov 2020 p51 q1
2679

Two ordinary fair dice, one red and the other blue, are thrown.

Event \(A\) is 'the score on the red die is divisible by 3'.

Event \(B\) is 'the sum of the two scores is at least 9'.

(a) Find \(P(A \cap B)\).

(b) Hence determine whether or not the events \(A\) and \(B\) are independent.

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June 2020 p52 q2
2680

A total of 500 students were asked which one of four colleges they attended and whether they preferred soccer or hockey. The numbers of students in each category are shown in the following table.

SoccerHockeyTotal
Amos543286
Benn8472156
Canton225678
Devar12060180
Total280220500

One of the students is chosen at random. Determine whether the events ‘the student prefers hockey’ and ‘the student is at Amos college or Benn college’ are independent, justifying your answer.

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Nov 2019 p63 q1
2681

There are 300 students at a music college. All students play exactly one of the guitar, the piano or the flute. The numbers of male and female students that play each of the instruments are given in the following table.

GuitarPianoFlute
Female students623543
Male students784042
  1. Find the probability that a randomly chosen student at the college is a male who does not play the piano. [1]
  2. Determine whether the events ‘a randomly chosen student is male’ and ‘a randomly chosen student does not play the piano’ are independent, justifying your answer. [2]
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June 2019 p62 q1
2682

Two ordinary fair dice are thrown and the numbers obtained are noted. Event S is ‘The sum of the numbers is even’. Event T is ‘The sum of the numbers is either less than 6 or a multiple of 4 or both’. Showing your working, determine whether the events S and T are independent.

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