Question

If the card drawn in first case is replaced, and the second boy draws a card. What is the probability of getting a prime number? A2/5 B4/5 C7/8 D9/11​

Answer 1

since the total no of cards are not given

let us assume  it is approximately 20 cards .

hence total outcomes is = 20

so we now find the prime number between 1 to 20.

it was (2,3,5,7,11,13,17,19)

i.e. total 8 numbers.

hence by drawing a prime number it is

=8/20

solving or simplifying we get

= 2/5

so option  (A) is the correct answer

Answer 2

Given:

Assuming there are $20$ cards in a pack.

To find:

The probability of getting a prime number

Formula:

$P(Getting\;a\;prime\;number)\;=\;\frac{Number\;of\;favourable\;outcomes}{Total\;number\;of\;possible\;outcomes}$

Step-by-step explanation:

The prime numbers from $1$ to $20$ are $2,3,5,7,11,13,17,19$

The number of favourable outcomes = $8$

The total number of outcomes = $20$

$P(Getting\;a\;prime\;number)\;=\;\frac{Number\;of\;favourable\;outcomes}{Total\;number\;of\;possible\;outcomes}$

⇒ $P(Getting\;a\;prime\;number)\;=\;\frac8{20}\;=\;\frac25$

Answer:

The probability of getting a prime number is $\frac{2}{5}$