Evaluate P10 2 19 90 45 8 C8 2 28 1440 720 4 se the addition

Evaluate. P_10, 2 19 90 45 8 C_8, 2 28 1440 720 4 se the addition principle for counting to solve the problem. If n(A) = 40, n(B) = 117 and n(A union B) = 137, what is n(A intersection B)? 10 20 22 40

Solution

21. P_10,2

We have to use permutation fornula here which is

P_n,r= n!/(n-r)!

Therefore

P_10,2= 10!/(10-2)! =10!/8!=90

Hence the correct option is B

22. We have to use the formula of combination here which is

C_n,r = n!/(r! *n-r)!)

Therefore

C_8,2 = 8!/ 2!(8-2)! =8!/(2! 6!) = 4*7=28

Hence the correct option is A