Why Is Calculating Card Probabilities Confusing?

[lorik]

Homework Statement

From 52 cards we draw one .Whats the probability that the drawn card is divisible by 4

Now : in my notebook its 12/52=3/13 .But shouldn't it be 13/52 ? BECAUSE clearly if we multiply 13 *4=52

Same problem : Whats the probability that of 52 cards I draw one that is divisible
with 10 or 11 .In notebook its like this P(a)+p(b)= 4/52+4/52=8/52=4/26=2/13

BUT shouldn't this as well be 5/52+5/52

Homework Equations

The Attempt at a Solution

PLEASE just tell the correct answer every time I post here somebody argues about pointless stuff and leaves me hanging with no clue !??

Sorry second problem fixed so 4/52+5/52 is correct ?

 

[berkeman]

Homework Statement

From 52 cards we draw one .Whats the probability that the drawn card is divisible by 4

Now : in my notebook its 12/52=3/13 .But shouldn't it be 13/52 ? BECAUSE clearly if we multiply 13 *4=52

Same problem : Whats the probability that of 52 cards I draw one that is divisible
with 10 or 11 .In notebook its like this P(a)+p(b)= 4/52+5/52=8/52=4/26=2/13

BUT shouldn't this as well be 5/52+5/52

Homework Equations

The Attempt at a Solution

PLEASE just tell the correct answer every time I post here somebody argues about pointless stuff and leaves me hanging with no clue !??

On the first one, your book is correct that there are 12 cards in the deck that have a value that is divisible by 4. What cards of each suit have a value that is divisible by 4?