Question

4. The blood groups of some students of Class IX were surveyed and recorded as below:
Blood Group
A
B
AB
0
No. of Students
19
6
13
12
If a student is chosen at random, find the probability that he/she has blood group A or AB.​

Answer 1

The blood groups of some students of Class IX were surveyed and recorded as below:

Blood Group       No. of Students

A                          19

B                          6

AB                       13

O                         12

Total                    50

We have to find, the probability that he/she has blood group A or AB.

Solution:

Here,

Total number of students = 50

Total number if possible outcomes = 50

For blood group A:

Number of students having blood A = 19

∴ P(A) = $\dfrac{Number of favourable outcomes}{All possible outcomes}$

P(A) = $\dfrac{19}{50}$

Thus, the probability that he/she has blood group A is $\dfrac{19}{50}$.

                                      OR:

For blood group AB:

Number of students having blood AB = 13

∴ P(AB) = $\dfrac{Number of favourable outcomes}{All possible outcomes}$

P(AB) = $\dfrac{13}{50}$

The probability that he/she has blood group A or AB(A ∪ AB)

= P(A) + P(AB)

= $\dfrac{19}{50}$ + $\dfrac{13}{50}$

= $\dfrac{32}{50}$

= $\dfrac{16}{25}$

Hence, the probability that he/she has blood group A or AB is" $\dfrac{16}{25}$".

Answer 2

Given :  The blood groups of some students of Class IX were surveyed and recorded

Blood Group    No. of Students

A                         19

B                          6

AB                        13

O                        12

a student is chosen at random

To Find :probability that he/she has blood group A or AB.​

Solution:

Total Students = 19 + 6 + 13 + 12 = 50

probability that he/she has blood group A or AB.​

P( A or AB)  = P(A) + P ( AB)

Because these events are mutually exclusive /disjoint events.

probability that he/she has blood group A or AB.​= P(A) + P ( AB)

P(A)  = 19/50

P(AB) = 13/50

probability that he/she has blood group A or AB.​= 19/50 + 13/50

= 32/50

= 16/25

= 0.64

probability that  random,  selected students has blood group A or AB.​ = 0.64

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