Question

Seventy cards are numbered 1 through 70 , one number per card. One card is randomly selected from the deck. What is the probability that the number drawn is a multiple of 3 AND a multiple of 5 ?

Answer 1

Answer:

$Probability = \frac{2}{35}$

Step-by-step explanation:

Given

$Total = 70$

First, we need to list the multiples of 5

$M_5 = \{5,10,15,20,25,30,35,40,45,50,55,60,65,70\}$

Then, multiples of 3$M_3 = \{3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60,63,66,69\}$

Next, is to list out the common elements in both

$M_3\ n\ M_5 = \{15,30,45,60\}$

$n(M_3\ n\ M_5) = 4$

The required probability is then calculated as thus:

$Probability = \frac{n(M_3\ n\ M_5)}{Total}$

$Probability = \frac{4}{70}$

$Probability = \frac{2}{35}$