How many times can abcd be arranged

If we fix A on first place and B on last place. Then second and third place can be filled in 1! So if the pair is on first and last place so we have only 1 way. So for C is on first place and D on last place we have 1 way. A is on first place and D. Either B is on second or third. And third position is filled with remaining.

Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Asked 4 years, 10 months ago. Manishearth Manishearth 1 1 gold badge 9 9 silver badges 31 31 bronze badges. Zeina Zeina 1 1 silver badge 9 9 bronze badges.

Sorry for not being clear enough. So in acbd, a is before b, and c is before d. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. Featured on Meta. Now live: A fully responsive profile. Linked 1.

Related 7. Hot Network Questions. Question feed. Permutation : It is the different arrangements of a given number of elements taken one by one, or some, or all at a time. The answer is 4! Combination : It is the different selections of a given number of elements taken one by one, or some, or all at a time. For example, if we have two elements A and B, then there is only one way select two items, we select both of them. Solution : In these type of questions, we assume all the vowels to be a single character, i.

But, R occurs 2 times. Solution : we assume all the vowels to be a single character, i. This article has been contributed by Nishant Arora.