TCS Company Numerical Ability Permutation and Combination

How many 9 digit numbers are possible by using the digits 1,2,3,4,5 which are divisible by 4 if the repetition is allowed?
a) 5^7 b) 5^6 c) 5^9 d) 5^8

Read Solution (Total 1)

_ _ _ _ _ _ _ _ _ (9 digit number)
Digits that can be used = 1, 2, 3, 4 and 5
For a number to divisible by 4, the last two digits have to be divisible by 4
So, the units digit cannot be 1, 3 or 5
If the units digit is 2, only 12, 32 adn 52 are acceptable as the last two digits
If the units digit is 4, only 24 and 44 are acceptable as the last two digits.
So, total 5 cases for the last two digits.
Now, the first 7 digits of the 9 digit number can be filled in 57 ways as each place can be filled by 1, 2, 3, 4 or 5.
So, desired answer = 57*5 = 58
13 years agoHelpfull: Yes(7) No(16)

TCS Other Question

It is dark in my bedroom and I want to get two socks of the same color from my drawer, which contains 24 red and 24 blue socks. How many socks do I have to take from the drawer to get at least two socks of the same color?
a) 2 b) 3 c) 48 d) 25 Given a collection of points P in the plane, a 1-set is a point in P that can be separated from the rest by a line, .i.e the point lies on one side of the line while the others lie on the other side.
The number of 1-sets of P is denoted by n1(P). The minimum value of n1(P) over all configurations P of 5 points in the plane in general position(.i.e no three points in P lie on a line) is

a)3 b)5 c) 2 d)1