UPSC NDA I 2021 Mathematics Solved Paper

Concept:
For the independent events A and B,
- P(A∪B)=P(A)+P(B)−P(A∩B)
- P(A∩B)=P(A)×P(B)
Calculation:
Probability of getting head on first toss P(E)=‌

1

2

Probability ofgetting head on first toss P(F)=‌

1

2

Since the events are independent P(E∩F)=P(E)×P(F)
P(E∩F)=‌

1

2

×‌

1

2

=‌

1

4

P(E∪F)=P(E)+P(F)−P(E∩F)
P(E∪F)=‌

1

2

+‌

1

2

−‌

1

4

P(E∪F)=‌

3

4