If a positive integer n is picked at random from the
positive integers less than or equal to 10, what is the 
probability that 5n + 3 ≤ 14?



Answer :

It is a good practice to solve this inequality first:
[tex] 5\cdot n + 3 \leq 14 [/tex]
[tex] 5\cdot n \leq 11 [/tex]
[tex] n \leq \frac{11}{5} [/tex]
[tex] \frac{11}{5} = 2.2 [/tex]
So we want to check, what is the probability, that this number is less than or equal to 2.2
Among 10 integers we have only 2 numbers that are less or equal to 2.2, namely 1 and 2. Therefore, the probability is:
[tex] \frac{2}{10}=\frac{1}{5} [/tex]