Is D really the correct ans ?
shouldn’t the ans be E
Yes, D is the correct answer. Let’s solve it.
First, question is asking about total distinct routes that she can take from work to home by stopping at grocery shop at middle. Now, use
permutation concept of repeats
. From work to grocery store routes is
[10!(total)/(4!(east steps repeated)x6!(nort steps repeated)]
. It will give the total distinct routes form work to grocery shop.
Second, calculate distinct routes from grocery shop to home which is
[9!(total)/6!(east steps repeated) x 3!(north step repeated)
At last, as we need total combination of these distinct routes, and we multiply these two result .The answer is D.
so you’ll need case 1 and 2