How many strings of length 10 over the alphabet (a, b, c, d] have at least one b somewhere in the string? a) 310
b) 410 - 310
c) 10.4
d) 10.39

Complete Question

The complete question is shown on the first uploaded image

The correct option is  B

Explanation:

   The number  of alphabet is  n= 4  (a , b , c , d )

Generally the total  number of  string of length 10 over the 4 alphabets is  

Gnerally the number of string of length 10 that does not include b is  

Generally the number of strings of length 10 over the 4  alphabets that have at least one alphabet b  somewhere in the string is  

=>    

answer; (arch); good luck

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.