Westonci.ca is your trusted source for finding answers to all your questions. Ask, explore, and learn with our expert community. Join our platform to connect with experts ready to provide precise answers to your questions in different areas. Our platform offers a seamless experience for finding reliable answers from a network of knowledgeable professionals.

how many bit-strings of length 12 contain a) exactly three 1s b) at most three 1s c) at least three 1s d) an equal number of zeros and ones?

Sagot :

a) Number of bit string = 220

b)  Number of bit string = 299

c)  Number of bit string = 4017

d)  Number of bit string = 924

What is Combination?

Combinations are mathematical operations that count the number of potential configurations for a set of elements when the order of the selection is irrelevant.

Given:

a) n= 12, r= 3

[tex]^{12}C_3[/tex] = 12! / 3! 9 !

      = 12 x 11 x 10 x 9! / 3 x 2 x 9!

      = 220

b)  n= 12, r ≤ 3

[tex]^{12}C_3[/tex] = 12! / 3! 9 !

      = 12 x 11 x 10 x 9! / 3 x 2 x 9!

      = 220

[tex]^{12}C_2[/tex] = 12! / 2! 10 !

      = 12 x 11 x 10! / 2 x 10!

      = 66

[tex]^{12}C_1[/tex] = 12! / 1! 11!

      = 12

[tex]^{12}C_0[/tex] = 12! / 0! 12 !

      = 12 x 11 x 10 x 9! / 3 x 2 x 9!

      = 1

So, total number of bit strings = 220 +66 + 12 +1 =299

c)  n= 12, r ≥ 3

[tex]^{12}C_3[/tex] = 12! / 3! 9 !

      = 12 x 11 x 10 x 9! / 3 x 2 x 9!

      = 220

[tex]^{12}C_4[/tex] = 495

[tex]^{12}C_5[/tex] = 792

[tex]^{12}C_6[/tex] = 924

[tex]^{12}C_7[/tex] = 792

[tex]^{12}C_8[/tex] = 495

[tex]^{12}C_9[/tex] = 220

[tex]^{12}C_{10[/tex] = 66

[tex]^{12}C_{12[/tex] = 12

[tex]^{12}C_{12[/tex] = 1

So, total String= 4017

d)  n= 12 and r= 6

[tex]^{12}C_6[/tex] = 12!/ 6! 6!

       = 12 x 11 x 10 x 9 x 8 x 7 x 6! / 6! 6!

       = 924

Learn more about Combination here:

https://brainly.com/question/28720645

#SPJ1