WB JEE 2019 | Permutations and Combinations Question 25 | Mathematics

WB JEE 2019

MCQ (Single Correct Answer)

-0.25

There are 7 greeting cards, each of a different colour and 7 envelopes of same 7 colours as that of the cards. The number of ways in which the cards can be put in envelopes, so that exactly 4 of the cards go into envelopes of respective colour is,

$${}^7{C_3}$$

2 . $${}^7{C_3}$$

3! $${}^4{C_4}$$

3! $${}^7{C_3}$$$${}^4{C_3}$$

WB JEE 2018

MCQ (Single Correct Answer)

-0.25

The number of selection of n objects from 2n objects of which n are identical and the rest are different, is

2ⁿ

2^{n $$-$$ 1}

2ⁿ $$-$$ 1

2^{n $$-$$ 1} + 1

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

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