Question

Te number of arrangements of 10 different things taken 4 at the time in which one particular thing always occurs is?

Answer 1

Answer:2016

Step-by-step explanation:

Number of different things = 10

Numbers of things which are taken at a time = 4

Now, it is said that one particular thing always occur.

So The question reduces to selecting 9 things from the 3 things

This can be done easily by using the concept of combinations

Number of ways selecting 3 things out of 9 different things such that one particular thing always occur =

Now, the 4th thing is fixed so number of ways for selecting the 4th thing = 4! = 24

Thus, Required number of ways = 84 × 24 = 2016

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