10th Maths Probability Exercise 13.1 Solutions

Exercise 13.1 Solutions – Class X Mathematics

Exercise 13.1 Solutions

Probability – Class X Mathematics

State Council of Educational Research and Training, Telangana, Hyderabad

Question 1: Complete the following statements

(i) Probability of an event \( E + \text{Probability of the event ‘not } E’ = \) ______.

Solution: The sum of the probability of an event and its complement is always 1.

\[ P(E) + P(\text{not } E) = 1 \]

(ii) The probability of an event that cannot happen is ______. Such an event is called ______.

Solution: The probability of an impossible event is 0. Such an event is called an impossible event.

\[ P(\text{Impossible event}) = 0 \]

(iii) The probability of an event that is certain to happen is ______. Such an event is called ______.

Solution: The probability of a certain event is 1. Such an event is called a sure event.

\[ P(\text{Certain event}) = 1 \]

(iv) The sum of the probabilities of all the elementary events of an experiment is ______.

Solution: The sum of probabilities of all elementary events of an experiment is 1.

\[ \sum P(E_i) = 1 \]

(v) The probability of an event is greater than or equal to ______ and less than or equal to ______.

Solution: The probability of any event \( E \) satisfies:

\[ 0 \leq P(E) \leq 1 \]

Question 2: Which of the following experiments have equally likely outcomes? Explain.

(i) A driver attempts to start a car. The car starts or does not start.

Solution: Not equally likely. The probability depends on the car’s condition, fuel, etc.

(ii) A player attempts to shoot a basketball. She/he shoots or misses the shot.

Solution: Not equally likely. The outcome depends on the player’s skill.

(iii) A trial is made to answer a true-false question. The answer is right or wrong.

Solution: Equally likely. There’s a 50% chance of guessing correctly.

\[ P(\text{Right}) = P(\text{Wrong}) = 0.5 \]

(iv) A baby is born. It is a boy or a girl.

Solution: Equally likely (assuming equal probability for biological sexes).

\[ P(\text{Boy}) = P(\text{Girl}) ≈ 0.5 \]

Question 3: If \( P(E) = 0.05 \), what is the probability of ‘not E’?

Solution:

We know that \( P(E) + P(\text{not } E) = 1 \)

\[ P(\text{not } E) = 1 – P(E) = 1 – 0.05 = 0.95 \]

Question 4: A bag contains lemon flavoured candies only. Malini takes out one candy without looking into the bag.

(i) an orange flavoured candy?

Solution: Since the bag contains only lemon flavored candies:

\[ P(\text{Orange}) = 0 \] (Impossible event)

(ii) a lemon flavoured candy?

Solution: Since all candies are lemon flavored:

\[ P(\text{Lemon}) = 1 \] (Certain event)

Diagram: A bag containing multiple lemon candies (all yellow) with one being drawn out.

[Illustration of a bag with yellow candies and one hand taking a candy out]

Question 5: Rahim removes all the hearts from the cards. What is the probability of:

i. Getting an ace from the remaining pack.

Solution: Original deck has 52 cards. After removing 13 hearts, 39 cards remain.

Number of aces in remaining cards: 3 (since Ace of Hearts was removed)

\[ P(\text{Ace}) = \frac{3}{39} = \frac{1}{13} \]

ii. Getting a diamonds.

Solution: All 13 diamonds remain in the deck of 39 cards.

\[ P(\text{Diamond}) = \frac{13}{39} = \frac{1}{3} \]

iii. Getting a card that is not a heart.

Solution: Since all hearts have been removed, all remaining 39 cards are not hearts.

\[ P(\text{Not heart}) = \frac{39}{39} = 1 \]

iv. Getting the Ace of hearts.

Solution: Since all hearts have been removed:

\[ P(\text{Ace of Hearts}) = 0 \] (Impossible event)

Diagram: A standard deck of cards with all heart cards (red) removed, showing only clubs, diamonds, and spades remaining.

[Illustration of a partial deck with hearts missing]

Question 6: In a group of 3 students, the probability of 2 students not having the same birthday is 0.992. What is the probability that the 2 students have the same birthday?

Solution:

Let \( P(\text{Same}) \) be the probability that two students share a birthday.

Given \( P(\text{Not same}) = 0.992 \)

\[ P(\text{Same}) = 1 – P(\text{Not same}) = 1 – 0.992 = 0.008 \]

Question 7: A die is rolled once. Find the probability of getting:

(i) a prime number

Solution: Prime numbers on a die: 2, 3, 5 (3 outcomes)

Total possible outcomes: 6

\[ P(\text{Prime}) = \frac{3}{6} = \frac{1}{2} \]

(ii) a number lying between 2 and 6

Solution: Numbers between 2 and 6: 3, 4, 5 (3 outcomes)

\[ P(\text{Between 2 and 6}) = \frac{3}{6} = \frac{1}{2} \]

(iii) an odd number

Solution: Odd numbers on a die: 1, 3, 5 (3 outcomes)

\[ P(\text{Odd}) = \frac{3}{6} = \frac{1}{2} \]

Diagram: A standard six-faced die showing numbers 1 through 6 with prime numbers (2,3,5) highlighted.

[Illustration of a die with some numbers highlighted]

Question 8: What is the probability of selecting a red king from a deck of cards?

Solution:

Total cards in deck: 52

Red kings: King of Hearts and King of Diamonds (2 cards)

\[ P(\text{Red King}) = \frac{2}{52} = \frac{1}{26} \]

Diagram: A deck of cards showing the two red kings (King of Hearts and King of Diamonds).

[Illustration of two red king cards]

Question 9: Make 5 more problems of this kind using dice, cards or birthdays

Sample Problems:

  1. What is the probability of rolling a number greater than 4 on a standard die?
  2. If two cards are drawn from a standard deck without replacement, what is the probability both are spades?
  3. In a group of 30 people, what is the probability that at least two people share the same birthday?
  4. What is the probability of drawing a face card (Jack, Queen, King) from a standard deck?
  5. If you roll two dice, what is the probability that the sum is 7?

These problems can be discussed with friends and teachers to understand probability concepts better.

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