JEE MAIN - Mathematics (2020 - 9th January Morning Slot - No. 6)

If the number of five digit numbers with distinct digits and 2 at the 10th place is 336 k, then k is equal to :
6
8
4
7

Explanation

JEE Main 2020 (Online) 9th January Morning Slot Mathematics - Permutations and Combinations Question 139 English Explanation

Except 1 and 2 there are eight options on first place and only one option at fourth place possible which is digit '2'.

Remaining three places can be filled by any three digits out of 1, 3, 4, 5, 6, 7, 8 and 9.

$$ \therefore $$ No. of five digits numbers = 8 $$ \times $$ 8 $$ \times $$ 7 $$ \times $$ 1 $$ \times $$ 6 = 336 $$ \times $$ 8

Also 336k = 336 $$ \times $$ 8

$$ \Rightarrow $$ k = 8

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