Permutation and combination question.

[vkash]

there are n students in a class. They are selected in sets of m. A student says he is selected a times. find value of a in terms of m and n.
Total number of selections made are ⁿC_m.
After that nothing is striking in my mind.can you please help.

 

[Ray Vickson]

there are n students in a class. They are selected in sets of m. A student says he is selected a times. find value of a in terms of m and n.
Total number of selections made are ⁿC_m.
After that nothing is striking in my mind.can you please help.

Start by looking at small example, such as n = 4 and m = 2, 3 or 4. Select an element such as '1', and look at all the subsets that contain that element. Once you see the pattern, it should be easier to look at the general n, m problem.

RGV

 

[vkash]

Start by looking at small example, such as n = 4 and m = 2, 3 or 4. Select an element such as '1', and look at all the subsets that contain that element. Once you see the pattern, it should be easier to look at the general n, m problem.

RGV

getting trend how it is happening and understanding how is it happening is different thing & i want to know second one not first one so it will helpful for me if you did it with variables.
so can anybody please do it with variables.

 

[Ray Vickson]

getting trend how it is happening and understanding how is it happening is different thing & i want to know second one not first one so it will helpful for me if you did it with variables.
so can anybody please do it with variables.

The forum rules require you to show your work. You have not done that.

RGV