$\"\"$

$\"\"$ objects named as $\"\"$ and $\"\"$ .

$\"\"$ objects are taken at a time from $\"\"$ objects.

The set of all the combinations is $\"\"$ .

Using definition of the combinations

$\"\"$

The total number of all the combinations is $\"\"$ .

$\"\"$

The set of all the combinations of $\"\"$ objects, taken $\"\"$ objects at a time is $\"\"$ .

The total number of all the combinations is $\"\"$ .