The Mathematics of Maybe: Introduction to Probability | Exercise 7.3

Question 3

In a village fair, there are 3 popular snacks available: Samosa, Pakora, and Bhaji. For drinks, villagers can choose either Chai or Lassi.

(i) List the sample space of all possible snack and drink combinations a person could choose at the fair.

(ii) List the event 'Selecting Samosa as a snack.'

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Solution

We will list all possible choices a person can make.

Step 1 — List all combinations

Let's list all snack and drink options. There are 3 snacks and 2 drinks. We combine each snack with each drink. This gives us all possible outcomes.

S={(Samosa, Chai),(Samosa, Lassi),(Pakora, Chai),(Pakora, Lassi),(Bhaji, Chai),(Bhaji, Lassi)}S = \{(\text{Samosa, Chai}), (\text{Samosa, Lassi}), (\text{Pakora, Chai}), (\text{Pakora, Lassi}), (\text{Bhaji, Chai}), (\text{Bhaji, Lassi})\}

The total number of outcomes is 6.

n(S)=6\boxed{n(S) = 6}

Diagram 1

Step 2 — Identify the event and its probability

We want the event 'Selecting Samosa as a snack'. Let's find outcomes where Samosa is chosen. These outcomes are (Samosa, Chai) and (Samosa, Lassi). There are 2 such outcomes.

E={(Samosa, Chai),(Samosa, Lassi)}E = \{(\text{Samosa, Chai}), (\text{Samosa, Lassi})\}

The number of outcomes in event E is 2. The probability is the number of favorable outcomes divided by total outcomes.

P(Samosa)=Number of outcomes in ETotal number of outcomesP(\text{Samosa}) = \frac{\text{Number of outcomes in E}}{\text{Total number of outcomes}}

P(Samosa)=26P(\text{Samosa}) = \frac{2}{6}

P(Samosa)=13P(\text{Samosa}) = \frac{1}{3}

P(Samosa)=13\boxed{P(\text{Samosa}) = \frac{1}{3}}

Answer

(i) The sample space is S={(Samosa, Chai),(Samosa, Lassi),(Pakora, Chai),(Pakora, Lassi),(Bhaji, Chai),(Bhaji, Lassi)}S = \{(\text{Samosa, Chai}), (\text{Samosa, Lassi}), (\text{Pakora, Chai}), (\text{Pakora, Lassi}), (\text{Bhaji, Chai}), (\text{Bhaji, Lassi})\}. The total number of outcomes is n(S)=6n(S) = 6. (ii) The event 'Selecting Samosa as a snack' is E={(Samosa, Chai),(Samosa, Lassi)}E = \{(\text{Samosa, Chai}), (\text{Samosa, Lassi})\}. The probability of this event is P(Samosa)=13P(\text{Samosa}) = \frac{1}{3}.

More questions in Exercise 7.3

Q1

When a single 6-sided die is rolled, what is the total number of possible outcomes in the sample space?

Q2

For the following experiments write down the sample space S.

(i) Rolling a die and tossing a coin together.

(ii) Choosing a random integer between – 5 and + 5.

(iii) A box containing 5 green and 7 red balls. One ball is drawn at random.

Q3

In a village fair, there are 3 popular snacks available: Samosa, Pakora, and Bhaji. For drinks, villagers can choose either Chai or Lassi.

(i) List the sample space of all possible snack and drink combinations a person could choose at the fair.

(ii) List the event 'Selecting Samosa as a snack.'

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