What is the probability that a number selected from 1 to 25 is a prime number when each of given number is equally likely to be selected?

Cards bearing non prime numbers are 1,4,6,8,9,10,12,14,15,16,18,20,21,22,24, 25

Total number of cards bearing non-prime numbers = 16

Number of favourable elementary events = 16

We know that , Probability = number of favourable elementary eventsTotal number of elementary events

So, P(getting a card bearing a non prime number) = 1625

Question 73 Probability Exercise 13.1

Next

Answer:

Solution:

When one event happens if and only if the other one doesn't, two occurrences are said to be complimentary. The probability of two complementary events add up to one.

Total no. of possible outcomes = 25 {1, 2, 3…. 25}

Let E = Event of getting a prime no.

So, the favourable outcomes are 2, 3, 5, 7, 11, 13, 17, 19, 23

No. of favourable outcomes = 9

Probability, P(E) = Number of favourable outcomes/ Total number of outcomes

P(E) = 9/25

The,

\overline{\mathrm{E}}=\text { Event of not getting a prime }

\begin{aligned} &P(\bar{E})=1-P(E) \\ &P(\bar{E})=1-\frac{9}{25} \\ &P(\bar{E})=\frac{16}{25} \end{aligned}

Therefore, the probability of selecting a number which is not prime is 16/25.

Was This helpful?