UPSC NDA Math Model Paper 1

Concept:
P(A: Not hitting the target )=1−P(A: hitting the target )
Calculations:
Person A can hit a target 4 times in 5 attempts. Person B−3 times in four attempts. Person C−2 times in 3 attempts.
P(A: hitting the target )=‌

4

5

⇒P(A: Not hitting the target )=‌

1

5

P(B: hitting the target )=‌

3

4

⇒P(B: Not hitting the target )=‌

1

5

P(C: hitting the target )=‌

2

3

⇒P(C: Not hitting the target )=‌

1

3

The probability that the target is hit atleast two times =P(A)P(B)P(C)+P(A)P(B)P(C) +P(A)P(B)P(C)+P(A)P(B)P(C)
⇒ The probability that the target is hit atleast two times =‌

1

5

+‌

1

10

+‌

2

15

+‌

2

5

⇒ The probability that the target is hit atleast two =‌

5

6