Question

13) In how many ways can 5 pens be selected from 10 different pens such that one particular pen is
never selected and one particular is always selected?
a) 56
b) 70
c) 126
d) None
14) A box contains 2 white balls, 3 black balls and 4 red balls. In how many ways can 3 halls he​

Answer 1

Answer:

selecting 4 from 8. There are 8*7*6*5=1680 ways of selections.

Explanation: There are only 5 places for the selected pens. However, 1 place is occupied(regarding ‘one particular pen is always selected’), so you just need to select 4 pens and must-select pen is excluded from the basket you select. And ‘one particular pen is never selected’, then only 8 pens are left for you choose. For the left 4 places, the first one comes from 8 choices, after finishing the first choice, only 7 pens left for choice. For the last place, only 5 pens left for choice. Therefore, all ways of selections come to be 8*7*6*5=1680.

Answer 2

Answer:

It would be 1680 ways