2.
People on the street were asked "How many siblings do you have?". The following diagram shows the result:
How many people answered the question?
Explanation
The diagram shows that the number of people who answered the question is 30.
3.
Use the grid to determine the probability of getting the sum 7 when two dice are rolled. (Express your answer as a fraction)
Explanation
We can get the sum 7 in six different ways, and the total outcomes when rolling two dice are 36. Hence P(sum 7) = 6/36 = 1/6
4.
People on the street were asked "How many siblings do you have?". The following diagram shows the result:
What's the mode?
Explanation
"Mode" isthe most frequently occurring value.
5.
Use the grid to determine which event has the highest probability: getting the sum 5 or getting the sum 10 when two dice are rolled?
Correct Answer
A. Getting the sum 5 is more likely
Explanation
We can get the sum 5 in four different ways and the sum 10 in only three different ways, and therefore P(sum 5) is greater than P(sum 10)
6.
You have received a phone number on a note, but the last digit in the number is missing!
073-309601....
Determine the probability that by choosing a random number for the last digit, you will get the correct phone number.
Correct Answer
1/10
0,10
0.10
10%
0,1
0.1
Explanation
Since there are 10 digits from 0-9 and only one is correct, the probability is 1/10 or 10% or 0,1
7.
A bag of marbles contains 5 black and 3 white marbles. You pick two marbles without looking (and no replacement).
Determine the probability that the first marble is black. (Express your answer as a fraction)
Correct Answer
5/8
Explanation
There are a total of 8 marbles, and 5 of them are black, hence the probability for black is 5/8.
8.
M=Male
F=Female
Use the tree diagram to determine the probability that a family with three children consists of three boys. (Express your answer as a fraction)
Correct Answer
1/8
Explanation
P(M)=1/2, hence P(M, M, M) = 1/2 x 1/2 x 1/2 = 1/8
9.
People on the street were asked "How many siblings do you have?". The following diagram shows the result:
What's the mean?
Correct Answer
1.3
1,3
Explanation
The mean is calculated by adding all the siblings together and then divide by the number of people participating. In this case: 0x5 + 1x15 + 2x7 + 3x2 + 4x1 = 39 and there were 30 people participating, so 39/30 = 1,3.
10.
People on the street were asked "How many siblings do you have?". The following diagram shows the result:
What's the median?
Correct Answer
1
Explanation
The median is the value in the middle when you order the data set from smallest number to the largest. In this case we know that we have 30 data values, so we will get two values in the middle - value nr15 and value nr16. By reading the diagram we find that value nr 15 and 16 are both the number 1, so the mean of these two values will be (1+1)/2 =1. Hence the median is 1.
11.
A bag with marbles contains 5 black and 3 white marbles. You pick two marbles without looking (and no replacement).
Determine the probability that both marbles are black. (Write as a fraction)
Correct Answer
20/56
10/28
5/14
Explanation
Probability for the first marble to be black is 5/8. Since there is no replacement the probability changes for the next one to be black, which is then 4/7. Product rule is used for compound events, hence the probability for black, black is: P(black, black) = 5/8 x 4/7 = 20/56 = 5/14
12.
M=Male
F=Female
Use the tree diagram to determine the probability that the children in a family with three children have different gender. (Express your answer as a fraction)
Correct Answer
6/8
3/4
Explanation
Each outcome has a probability of 1/8, and there can be different genders in 6 different ways. So P(different genders) = 6/8 = 3/4
13.
All students in a town were tested for colour blindness:
Normal vision: Boys 9800 Girls 9360
Colour blind: Boys 720 Girls 120
a) Determine the probability that a girl is colour blind. (Express your answer in percentage form)
Correct Answer
1,3%
1.3%
Explanation
120 girls were colour blind and there were a total of 9480 girls. The probability is then 120/9480 = 0,0126 = 1,3%
14.
All students in a town were tested for colour blindness:
Normal vision: Boys 9800 Girls 9360
Colour blind: Boys 720 Girls 120
a) Determine the probability that a boy is colour blind. (Express your answer in percentage form with one decimal)
Correct Answer
6,8%
6.8%
Explanation
720 boys were colour blind and there were a total of 10520 boys.. The probability is then 720/10520 = 0,068 = 6,8%
15.
There are 4 grey socks, 4 black socks and 4 white socks in a drawer. You pick two socks without looking (and without replacement). What are chances that both socks have the same colour? (Draw a tree diagram and then express your answer as a fraction.)
Correct Answer
3/11
16.
You plant three seeds. The chance for a seed to grow is 80%. Determine the probability that no seed grows. (Express your answer in percentage form)
Correct Answer
0,8%
0.8%
Explanation
P(one seed will not grow)=20% = 0,2
P(all three seeds will not grow) = 0,2 x 0,2 x 0,2 = 0,008 = 0,8%
17.
You plant three seeds. The chance for a seed to grow is 80%. Determine the probability that at least one seed grows. (Express your answer in percentage form)
Correct Answer
99,2%
99.2%
Explanation
"At least one seed grows" is complementary event to "not one seed will grow".
Since P(not one seed will grow) = 0,2 x 0,2 x 0,2 = 0,008 then P(at least one seed will grow) = 1 - 0,008 = 0,992 = 99,2%