First slide

Theorems of probability

Question

A pair of numbers is picked up randomly (without replacement) from the set {1, 2, 3,5, 7, 11, 12, 13, 17, 19). The probability that the number 11 was picked given that the sum of the numbers was even is nearly

Moderate

A

0.1
B

0.125
C

0.24
D

0.18

Solution

Let Abe the event that 11 is picked and B be the event that sum is even. The number of ways of selecting 11 along with one more odd number is $n (A \cap B) =^{7} C_{1}$ .
The number of ways of selecting either two even numbers or selecting two odd numbers is $n (B) = 1 +^{8} C_{2}$ .
$∴ P (A / B) = \frac{P (A \cap B)}{P (B)} = \frac{7}{29} = 0 .24$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App