Question

the probabilities of a student getting grades a b c and d are 0.2 0.3 0.15 and 0.35 respectively then find the probability that a student gets at least C grade

Answer 1

P(A)=0.2; P(B)=0.3; P(C)=0.15; P(D)=0.35;

At least grade C means, the student can get either A, B or C.
So P(AUBUC)=P(A)+P(B)+P(C)=0.2+0.3+0.15=0.65.

Answer 2

Answer:

Probability(at least grade C) = 0.65

Step-by-step explanation:

P(grade A) = 0.2

P(grade B)=0.3

P(grade C)=0.15

P(grade D)=0.35

Now, if a student has to score at least grade C. So, the student can score either grade A, grade B, or grade C but not grade D

So, to calculate Probability of scoring at least grade C : We add probabilities of scoring grade A, grade B and grade C

⇒ P(A U B U C) = P(A) + P(B) + P(C)

                          = 0.2 + 0.3 + 0.15

                           = 0.65

Hence, Probability(at least grade C) = 0.65