a,b,c

SET A=2,3,5,6,7;
>1st assume c is 5
then M1 =3c3=1
>2nd assume c is 6
then M2 = 2c1+1c1 (1st b is 5; 2nd b is 3) =2+1=3
3rd assume c is 7
> then M3=3c1+2c1+1c1=3+2+1=6

M=1+3+6 =10

similarlly, N=1+2+3=6
M-N=10-6 =4

answer 4

shashank.ism wrote:Three elements a, b and c are selected from the set A = 2, 3, 5, 6, 7 to form a three-digit number ‘abc’, where a < b < c. Similarly, two elements p and q are selected from the set B = 0, 1, 8, 9 to form a two-digit number ‘pq’, where p > q. Let, M be the total number of all the possible values of ‘abc’ and N be the total number of all the possible values of ‘pq’. What is the value of (M – N)?


7
6
5
4
1

abc can be formed in 5C3 ways and there can be only 1 way to arrange them in dec order so tot 10 ways for M

pq can be formed in 3C1 * 3C1=9 ways

M-N=1

OA pls

shashank.ism wrote:Three elements a, b and c are selected from the set A = 2, 3, 5, 6, 7 to form a three-digit number ‘abc’, where a < b < c. Similarly, two elements p and q are selected from the set B = 0, 1, 8, 9 to form a two-digit number ‘pq’, where p > q. Let, M be the total number of all the possible values of ‘abc’ and N be the total number of all the possible values of ‘pq’. What is the value of (M – N)?


7
6
5
4
1

Since,the order of the no.s are given(ascending or descending)no permutations can be done and the any unique selection will determine that particular no.
Thus,for abc we have 5C3 = 10
For pq we have 4C2 = 6
[spoiler]Hence, M = 10 - 6 =4 .D is[/spoiler] the ans.

thephoenix wrote:

shashank.ism wrote:Three elements a, b and c are selected from the set A = 2, 3, 5, 6, 7 to form a three-digit number ‘abc’, where a < b < c. Similarly, two elements p and q are selected from the set B = 0, 1, 8, 9 to form a two-digit number ‘pq’, where p > q. Let, M be the total number of all the possible values of ‘abc’ and N be the total number of all the possible values of ‘pq’. What is the value of (M – N)?


7
6
5
4
1

abc can be formed in 5C3 ways and there can be only 1 way to arrange them in dec order so tot 10 ways for M

pq can be formed in 3C1 * 3C1=9 ways

M-N=1

OA pls

Hey the phoenix ,
I think you made a mistake over there.

abc can be formed in 5C3 ways and there can be only 1 way to arrange them in dec order so tot 10 ways for M

Similarly,we have to consider for pq also.I see you adopted a different aproach for pq whereas the approach for abc(5C3) can also be implemented for pq(4C2).

pq can be formed in 3C1 * 3C1=9 ways

From what I can make out,I think your approach was like this.

Since,we have a zero,it cannot fill the tens digit as we have to construct a 2-digit no.
Hence,tens digit can be filled in 3C1 ways.
Corresponding to it,the units place can be filled in 3C1 ways.
Hence,the answer is 3C1*3C1 ways = 9 ways.
Hence ,M-N=1

But over here,you also took the case when the tens place had 1 and the units place 8.Thus pq being 18.
But,in the ques. it is given that p>q.Over here,1 is not greater than 8.
So,I guess over here you took some extra cases.
Hope this post helps in figuring out the mistake.


Also,shashank can you post the OA and the soln. plz!!