Q. The probabilities that a student will obtain grades $A,B,C\ or\ D$ are 0.30, 0.35, 0.20 and 0.15 respectively. The probability that he will receive atleast $C$ grade, is
A) 0.65
B) 0.85
C) 0.80
D) 0.20
Explanation
(d)
Grade order is $A > B > C > D$
For atleast $C$ grade, he will get grade $A$ or grade $B$ or grade $C$
$\therefore$ Required probability $= 0.30 + 0.35 + 0.20 = 0.85$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.