WB JEE 2018 | Permutations and Combinations Question 23 | Mathematics

WB JEE 2018

MCQ (Single Correct Answer)

-0.25

If (2 $$ \le $$ r $$ \le $$ n), then $${}^n{C_r}$$ + 2 . $${}^n{C_{r + 1}}$$ + $${}^n{C_{r + 2}}$$ is equal to

2 . $${}^n{C_{r + 2}}$$

$${}^{n + 1}{C_{r + 1}}$$

$${}^{n + 2}{C_{r + 2}}$$

$${}^{n + 1}{C_r}$$

WB JEE 2018

MCQ (Single Correct Answer)

-0.5

From a collection of 20 consecutive natural numbers, four are selected such that they are not consecutive. The number of such selections is

284 $$ \times $$ 17

285 $$ \times $$ 17

284 $$ \times $$ 16

285 $$ \times $$ 16

WB JEE 2017

MCQ (Single Correct Answer)

-0.25

The number of all numbers having 5 digits, with distinct digits is

99999

$$9 \times {}^9{P_4}$$

$${}^{10}{P_5}$$

$${}^9{P_4}$$

WB JEE 2017

MCQ (Single Correct Answer)

-0.25

Out of 7 consonants and 4 vowels, words are formed each having 3 consonants and 2 vowels. The number of such words that can be formed is

210

25200

2520

302400

WB JEE Subjects