Question

Twenty tickets are marked the numbers 1, 2, ..... 20. If three tickets be drawn at random, then what is the probability that those marked 7 and 11 are among them

• A. $\frac { 3 } { 190 }$
• B. $\frac { 1 } { 19 }$
• C. $\frac { 1 } { 190 }$
• D. None of these

Answer 1

Answer: (A)

$\frac { 3 } { 190 }$

Answer 2

7,11 have always to be in that group of three, therefore 3rd ticket may be chosen in 18 ways.

Hence required probability is .